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add translation for dart.
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hanguokai
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@ -9,7 +9,7 @@ translators:
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Dart 是编程语言王国的新人。
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它借鉴了许多其他主流语言，并且不会偏离它的兄弟语言 JavaScript 太多。
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就像 JavaScript，Dart 的目标是提供良好的浏览器集成。
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就像 JavaScript 一样，Dart 的目标是提供良好的浏览器集成。
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Dart 最有争议的特性必然是它的可选类型。
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@ -17,15 +17,14 @@ Dart 最有争议的特性必然是它的可选类型。
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import "dart:collection";
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import "dart:math" as DM;
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// Welcome to Learn Dart in 15 minutes. http://www.dartlang.org/
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// This is an executable tutorial. You can run it with Dart or on
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// the Try Dart! site if you copy/paste it there. http://try.dartlang.org/
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// 欢迎进入15分钟的 Dart 学习。 http://www.dartlang.org/
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// 这是一个可实际执行的向导。你可以用 Dart 运行它
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// 或者在线执行! 可以把代码复制/粘贴到这个网站。 http://try.dartlang.org/
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// Function declaration and method declaration look the same. Function
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// declarations can be nested. The declaration takes the form of
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// name() {} or name() => singleLineExpression;
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// The fat arrow function declaration has an implicit return for the result of
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// the expression.
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// 函数声明和方法声明看起来一样。
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// 函数声明可以嵌套。声明使用这种 name() {} 的形式，
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// 或者 name() => 单行表达式; 的形式。
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// 右箭头的声明形式会隐式地返回表达式的结果。
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example1() {
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example1nested1() {
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example1nested2() => print("Example1 nested 1 nested 2");
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@ -34,7 +33,7 @@ example1() {
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example1nested1();
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}
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// Anonymous functions don't include a name.
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// 匿名函数没有函数名。
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example2() {
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example2nested1(fn) {
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fn();
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@ -42,21 +41,20 @@ example2() {
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example2nested1(() => print("Example2 nested 1"));
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}
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// When a function parameter is declared, the declaration can include the
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// number of parameters the function takes by specifying the names of the
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// parameters it takes.
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// 当声明函数类型的参数的时候，声明中可以包含
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// 函数参数需要的参数，指定所需的参数名即可。
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example3() {
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example3nested1(fn(informSomething)) {
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fn("Example3 nested 1");
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}
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example3planB(fn) { // Or don't declare number of parameters.
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example3planB(fn) { // 或者不声明函数参数的参数
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fn("Example3 plan B");
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}
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example3nested1((s) => print(s));
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example3planB((s) => print(s));
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}
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// Functions have closure access to outer variables.
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// 函数有可以访问到外层变量的闭包。
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var example4Something = "Example4 nested 1";
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example4() {
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example4nested1(fn(informSomething)) {
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@ -65,8 +63,8 @@ example4() {
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example4nested1((s) => print(s));
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}
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// Class declaration with a sayIt method, which also has closure access
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// to the outer variable as though it were a function as seen before.
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// 下面这个包含 sayIt 方法的类声明，同样有一个可以访问外层变量的闭包，
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// 就像前面的函数一样。
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var example5method = "Example5 sayIt";
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class Example5Class {
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sayIt() {
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@ -74,14 +72,14 @@ class Example5Class {
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}
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}
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example5() {
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// Create an anonymous instance of the Example5Class and call the sayIt
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// method on it.
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// 创建一个 Example5Class 类的匿名实例，
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// 并调用它的 sayIt 方法。
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new Example5Class().sayIt();
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}
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// Class declaration takes the form of class name { [classBody] }.
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// Where classBody can include instance methods and variables, but also
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// class methods and variables.
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// 类的声明使用这种形式 class name { [classBody] }.
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// classBody 中可以包含实例方法和变量，
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// 还可以包含类方法和变量。
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class Example6Class {
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var example6InstanceVariable = "Example6 instance variable";
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sayIt() {
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@ -92,7 +90,7 @@ example6() {
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new Example6Class().sayIt();
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}
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// Class methods and variables are declared with "static" terms.
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// 类方法和变量使用 static 关键词声明。
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class Example7Class {
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static var example7ClassVariable = "Example7 class variable";
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static sayItFromClass() {
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@ -107,11 +105,10 @@ example7() {
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new Example7Class().sayItFromInstance();
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}
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// Literals are great, but there's a restriction for what literals can be
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// outside of function/method bodies. Literals on the outer scope of class
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// or outside of class have to be constant. Strings and numbers are constant
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// by default. But arrays and maps are not. They can be made constant by
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// declaring them "const".
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// 字面量非常方便，但是对于在函数/方法的外层的字面量有一个限制，
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// 类的外层或外面的字面量必需是常量。
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// 字符串和数字默认是常量。
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// 但是 array 和 map 不是。他们需要用 "const" 声明为常量。
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var example8A = const ["Example8 const array"],
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example8M = const {"someKey": "Example8 const map"};
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example8() {
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@ -119,9 +116,9 @@ example8() {
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print(example8M["someKey"]);
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}
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// Loops in Dart take the form of standard for () {} or while () {} loops,
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// slightly more modern for (.. in ..) {}, or functional callbacks with many
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// supported features, starting with forEach.
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// Dart 中的循环使用标准的 for () {} 或 while () {} 的形式，
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// 以及更加现代的 for (.. in ..) {} 的形式, 或者
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// 以 forEach 开头并具有许多特性支持的函数回调的形式。
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var example9A = const ["a", "b"];
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example9() {
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for (var i = 0; i < example9A.length; i++) {
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@ -138,7 +135,7 @@ example9() {
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example9A.forEach((e) => print("Example9 forEach loop '${e}'"));
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}
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// To loop over the characters of a string or to extract a substring.
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// 遍历字符串中的每个字符或者提取其子串。
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var example10S = "ab";
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example10() {
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for (var i = 0; i < example10S.length; i++) {
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@ -149,14 +146,14 @@ example10() {
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}
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}
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// Int and double are the two supported number formats.
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// 支持两种数字格式 int 和 double 。
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example11() {
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var i = 1 + 320, d = 3.2 + 0.01;
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print("Example11 int ${i}");
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print("Example11 double ${d}");
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}
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// DateTime provides date/time arithmetic.
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// DateTime 提供了日期/时间的算法。
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example12() {
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var now = new DateTime.now();
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print("Example12 now '${now}'");
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@ -164,7 +161,7 @@ example12() {
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print("Example12 tomorrow '${now}'");
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}
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// Regular expressions are supported.
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// 支持正则表达式。
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example13() {
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var s1 = "some string", s2 = "some", re = new RegExp("^s.+?g\$");
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match(s) {
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@ -178,8 +175,8 @@ example13() {
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match(s2);
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}
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// Boolean expressions need to resolve to either true or false, as no
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// implicit conversions are supported.
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// 布尔表达式必需被解析为 true 或 false，
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// 因为不支持隐式转换。
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example14() {
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var v = true;
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if (v) {
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@ -188,17 +185,17 @@ example14() {
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v = null;
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try {
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if (v) {
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// Never runs
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// 不会执行
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} else {
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// Never runs
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// 不会执行
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}
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} catch (e) {
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print("Example14 null value causes an exception: '${e}'");
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}
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}
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// try/catch/finally and throw are used for exception handling.
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// throw takes any object as parameter;
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// try/catch/finally 和 throw 语句用于异常处理。
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// throw 语句可以使用任何对象作为参数。
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example15() {
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try {
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try {
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@ -214,8 +211,8 @@ example15() {
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}
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}
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// To be efficient when creating a long string dynamically, use
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// StringBuffer. Or you could join a string array.
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// 要想有效地动态创建长字符串，
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// 应该使用 StringBuffer。 或者 join 一个字符串的数组。
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example16() {
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var sb = new StringBuffer(), a = ["a", "b", "c", "d"], e;
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for (e in a) { sb.write(e); }
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@ -224,8 +221,8 @@ example16() {
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print("Example16 join string array '${a.join()}'");
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}
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// Strings can be concatenated by just having string literals next to
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// one another with no further operator needed.
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// 字符串连接只需让相邻的字符串字面量挨着，
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// 不需要额外的操作符。
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example17() {
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print("Example17 "
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"concatenate "
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@ -233,44 +230,41 @@ example17() {
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"just like that");
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}
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// Strings have single-quote or double-quote for delimiters with no
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// actual difference between the two. The given flexibility can be good
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// to avoid the need to escape content that matches the delimiter being
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// used. For example, double-quotes of HTML attributes if the string
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// contains HTML content.
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// 字符串使用单引号或双引号做分隔符，二者并没有实际的差异。
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// 这种灵活性可以很好地避免内容中需要转义分隔符的情况。
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// 例如，字符串内容里的 HTML 属性使用了双引号。
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example18() {
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print('Example18 <a href="etc">'
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"Don't can't I'm Etc"
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'</a>');
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}
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// Strings with triple single-quotes or triple double-quotes span
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// multiple lines and include line delimiters.
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// 用三个单引号或三个双引号表示的字符串
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// 可以跨越多行，并且包含行分隔符。
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example19() {
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print('''Example19 <a href="etc">
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Example19 Don't can't I'm Etc
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Example19 </a>''');
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}
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// Strings have the nice interpolation feature with the $ character.
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// With $ { [expression] }, the return of the expression is interpolated.
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// $ followed by a variable name interpolates the content of that variable.
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// $ can be escaped like so \$ to just add it to the string instead.
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// 字符串可以使用 $ 字符插入内容。
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// 使用 $ { [expression] } 的形式，表达式的值会被插入到字符串中。
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// $ 跟着一个变量名会插入变量的值。
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// 如果要在字符串中插入 $ ，可以使用 \$ 的转义形式代替。
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example20() {
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var s1 = "'\${s}'", s2 = "'\$s'";
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print("Example20 \$ interpolation ${s1} or $s2 works.");
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}
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// Optional types allow for the annotation of APIs and come to the aid of
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// IDEs so the IDEs can better refactor, auto-complete and check for
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// errors. So far we haven't declared any types and the programs have
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// worked just fine. In fact, types are disregarded during runtime.
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// Types can even be wrong and the program will still be given the
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// benefit of the doubt and be run as though the types didn't matter.
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// There's a runtime parameter that checks for type errors which is
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// the checked mode, which is said to be useful during development time,
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// but which is also slower because of the extra checking and is thus
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// avoided during deployment runtime.
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// 可选类型允许作为 API 的标注，并且可以辅助 IDE，
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// 这样 IDE 可以更好地提供重构、自动完成和错误检测功能。
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// 目前为止我们还没有声明任何类型，并且程序运行地很好。
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// 事实上，类型在运行时会被忽略。
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// 类型甚至可以是错的，并且程序依然可以执行，
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// 好像和类型完全无关一样。
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// 有一个运行时参数可以让程序进入检查模式，它会在运行时检查类型错误。
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// 这在开发时很有用，但是由于增加了额外的检查会使程序变慢，
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// 因此应该避免在部署时使用。
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class Example21 {
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List<String> _names;
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Example21() {
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@ -293,7 +287,7 @@ void example21() {
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print("Example21 names '${o.names}' and length '${o.length}'");
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}
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// Class inheritance takes the form of class name extends AnotherClassName {}.
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// 类的继承形式是 class name extends AnotherClassName {} 。
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class Example22A {
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var _name = "Some Name!";
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get name => _name;
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@ -304,13 +298,13 @@ example22() {
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print("Example22 class inheritance '${o.name}'");
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}
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// Class mixin is also available, and takes the form of
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// 类也可以使用 mixin 的形式 ：
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// class name extends SomeClass with AnotherClassName {}.
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// It's necessary to extend some class to be able to mixin another one.
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// The template class of mixin cannot at the moment have a constructor.
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// Mixin is mostly used to share methods with distant classes, so the
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// single inheritance doesn't get in the way of reusable code.
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// Mixins follow the "with" statement during the class declaration.
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// 必需继承某个类才能 mixin 另一个类。
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// 当前 mixin 的模板类不能有构造函数。
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// Mixin 主要是用来和辅助的类共享方法的，
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// 这样单一继承就不会影响代码复用。
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// Mixin 声明在类定义的 "with" 关键词后面。
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class Example23A {}
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class Example23Utils {
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addTwo(n1, n2) {
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@ -329,10 +323,9 @@ example23() {
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print("Example23 addTwo(1, 2) results in '${r2}'");
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}
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// The Class constructor method uses the same name of the class and
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// takes the form of SomeClass() : super() {}, where the ": super()"
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// part is optional and it's used to delegate constant parameters to the
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// super-parent's constructor.
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// 类的构造函数名和类名相同，形式为
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// SomeClass() : super() {}, 其中 ": super()" 的部分是可选的，
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// 它用来传递参数给父类的构造函数。
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class Example24A {
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var _value;
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Example24A({value: "someValue"}) {
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@ -350,9 +343,9 @@ example24() {
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print("Example24 calling super during constructor '${o2.value}'");
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}
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// There's a shortcut to set constructor parameters in case of simpler classes.
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// Just use the this.parameterName prefix and it will set the parameter on
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// an instance variable of same name.
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// 对于简单的类，有一种设置构造函数参数的快捷方式。
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// 只需要使用 this.parameterName 的前缀，
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// 它就会把参数设置为同名的实例变量。
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class Example25 {
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var value, anotherValue;
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Example25({this.value, this.anotherValue});
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@ -363,9 +356,9 @@ example25() {
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"'${o.anotherValue}'");
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}
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// Named parameters are available when declared between {}.
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// Parameter order can be optional when declared between {}.
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// Parameters can be made optional when declared between [].
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// 可以在大括号 {} 中声明命名参数。
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// 大括号 {} 中声明的参数的顺序是随意的。
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// 在中括号 [] 中声明的参数也是可选的。
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example26() {
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var _name, _surname, _email;
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setConfig1({name, surname}) {
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@ -385,13 +378,11 @@ example26() {
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"email '${_email}'");
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}
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// Variables declared with final can only be set once.
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// In case of classes, final instance variables can be set via constant
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// constructor parameter.
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// 使用 final 声明的变量只能被设置一次。
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// 在类里面，final 实例变量可以通过常量的构造函数参数设置。
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class Example27 {
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final color1, color2;
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// A little flexibility to set final instance variables with syntax
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// that follows the :
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// 更灵活一点的方法是在冒号 : 后面设置 final 实例变量。
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Example27({this.color1, color2}) : color2 = color2;
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}
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example27() {
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@ -400,11 +391,11 @@ example27() {
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print("Example27 color is '${o.color1}' and '${o.color2}'");
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}
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// To import a library, use import "libraryPath" or if it's a core library,
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// import "dart:libraryName". There's also the "pub" package management with
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// its own convention of import "package:packageName".
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// See import "dart:collection"; at the top. Imports must come before
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// other code declarations. IterableBase comes from dart:collection.
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// 要导入一个库，使用 import "libraryPath" 的形式，或者如果要导入的是
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// 核心库使用 import "dart:libraryName" 。还有一个称为 "pub" 的包管理工具，
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// 它使用 import "package:packageName" 的约定形式。
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// 看下这个文件顶部的 import "dart:collection"; 语句。
|
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// 导入语句必需在其它代码声明之前出现。IterableBase 来自于 dart:collection 。
|
||||
class Example28 extends IterableBase {
|
||||
var names;
|
||||
Example28() {
|
||||
@ -417,11 +408,11 @@ example28() {
|
||||
o.forEach((name) => print("Example28 '${name}'"));
|
||||
}
|
||||
|
||||
// For control flow we have:
|
||||
// * standard switch with must break statements
|
||||
// * if-else if-else and ternary ..?..:.. operator
|
||||
// * closures and anonymous functions
|
||||
// * break, continue and return statements
|
||||
// 对于控制流语句，我们有：
|
||||
// * 必需带 break 的标准 switch 语句
|
||||
// * if-else 和三元操作符 ..?..:..
|
||||
// * 闭包和匿名函数
|
||||
// * break, continue 和 return 语句
|
||||
example29() {
|
||||
var v = true ? 30 : 60;
|
||||
switch (v) {
|
||||
@ -448,12 +439,12 @@ example29() {
|
||||
} else {
|
||||
continue;
|
||||
}
|
||||
// Never gets here.
|
||||
// 不会到这里。
|
||||
}
|
||||
}
|
||||
|
||||
// Parse int, convert double to int, or just keep int when dividing numbers
|
||||
// by using the ~/ operation. Let's play a guess game too.
|
||||
// 解析 int，把 double 转成 int，或者使用 ~/ 操作符在除法计算时仅保留整数位。
|
||||
// 让我们也来场猜数游戏吧。
|
||||
example30() {
|
||||
var gn, tooHigh = false,
|
||||
n, n2 = (2.0).toInt(), top = int.parse("123") ~/ n2, bottom = 0;
|
||||
@ -481,11 +472,9 @@ example30() {
|
||||
}
|
||||
}
|
||||
|
||||
// Programs have only one entry point in the main function.
|
||||
// Nothing is expected to be executed on the outer scope before a program
|
||||
// starts running with what's in its main function.
|
||||
// This helps with faster loading and even lazily loading of just what
|
||||
// the program needs to startup with.
|
||||
// 程序的唯一入口点是 main 函数。
|
||||
// 在程序开始执行 main 函数之前，不期望执行任何外层代码。
|
||||
// 这样可以帮助程序更快地加载，甚至仅惰性加载程序启动时需要的部分。
|
||||
main() {
|
||||
print("Learn Dart in 15 minutes!");
|
||||
[example1, example2, example3, example4, example5, example6, example7,
|
||||
@ -500,8 +489,8 @@ main() {
|
||||
|
||||
## 延伸阅读
|
||||
|
||||
Dart 有一个全面的网站。它涵盖了 API 参考、入门向导、文章以及更多，
|
||||
包括一个有用的 Dart 在线试用。
|
||||
Dart 有一个综合性网站。它涵盖了 API 参考、入门向导、文章以及更多，
|
||||
还包括一个有用的在线试用 Dart 页面。
|
||||
http://www.dartlang.org/
|
||||
http://try.dartlang.org/
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user