查看“TypeScript 接口”的源代码

{{DISPLAYTITLE:TypeScript 接口}}[[Category:TypeScript 教程|16]]
= TypeScript 接口 =

接口是一系列抽象方法的声明，是一些方法特征的集合，这些方法都应该是抽象的，需要由具体的类去实现，然后第三方就可以通过这组抽象方法调用，让具体的类执行具体的方法。

TypeScript 接口定义如下：

<pre>interface interface_name {
}</pre>
==

以下实例中，我们定义了一个接口 IPerson，接着定义了一个变量 customer，它的类型是 IPerson。

customer 实现了接口 IPerson 的属性和方法。

== TypeScript ==

<sample title="" desc="" lang="typescript" hererun="1"> interface IPerson {
    firstName:string,
    lastName:string,
    sayHi: ()=>string
}

var customer:IPerson = {
    firstName:"Tom",
    lastName:"Hanks",
    sayHi: ():string =>{return "Hi there"}
}

console.log("Customer 对象 ")
console.log(customer.firstName)
console.log(customer.lastName)
console.log(customer.sayHi())

var employee:IPerson = {
    firstName:"Jim",
    lastName:"Blakes",
    sayHi: ():string =>{return "Hello!!!"}
}

console.log("Employee  对象 ")
console.log(employee.firstName)
console.log(employee.lastName) </sample>
需要注意接口不能转换为 JavaScript。 它只是 TypeScript 的一部分。

编译以上代码，得到以下 JavaScript 代码：

== JavaScript ==

<sample title="" desc="" lang="typescript" hererun="1"> var customer = {
    firstName: "Tom",
    lastName: "Hanks",
    sayHi: function () { return "Hi there"; }
};
console.log("Customer 对象 ");
console.log(customer.firstName);
console.log(customer.lastName);
console.log(customer.sayHi());
var employee = {
    firstName: "Jim",
    lastName: "Blakes",
    sayHi: function () { return "Hello!!!"; }
};
console.log("Employee  对象 ");
console.log(employee.firstName);
console.log(employee.lastName); </sample>
输出结果为：

<pre>Customer 对象
Tom
Hanks
Hi there
Employee  对象
Jim
Blakes</pre>
== 联合类型和接口 ==

以下实例演示了如何在接口中使用联合类型：

== TypeScript ==

<sample title="" desc="" lang="typescript" hererun="1"> interface RunOptions {
    program:string;
    commandline:string[]|string|(()=>string);
}

// commandline 是字符串
var options:RunOptions = {program:"test1",commandline:"Hello"};
console.log(options.commandline)

// commandline 是字符串数组
options = {program:"test1",commandline:["Hello","World"]};
console.log(options.commandline[0]);
console.log(options.commandline[1]);

// commandline 是一个函数表达式
options = {program:"test1",commandline:()=>{return "**Hello World**";}};

var fn:any = options.commandline;
console.log(fn()); </sample>
编译以上代码，得到以下 JavaScript 代码：

== JavaScript ==

<sample title="" desc="" lang="typescript" hererun="1"> // commandline 是字符串
var options = { program: "test1", commandline: "Hello" };
console.log(options.commandline);
// commandline 是字符串数组
options = { program: "test1", commandline: ["Hello", "World"] };
console.log(options.commandline[0]);
console.log(options.commandline[1]);
// commandline 是一个函数表达式
options = { program: "test1", commandline: function () { return "**Hello World**"; } };
var fn = options.commandline;
console.log(fn()); </sample>
输出结果为：

<pre>Hello
Hello
World
**Hello World**</pre>
== 接口和数组 ==

接口中我们可以将数组的索引值和元素设置为不同类型，索引值可以是数字或字符串。

设置元素为字符串类型：

<sample title="" desc="" lang="typescript" hererun="1"> interface namelist {
   [index:number]:string
}

// 类型一致，正确
var list2:namelist = ["Google","xiaoBai","Taobao"]
// 错误元素 1 不是 string 类型
// var list2:namelist = ["xiaoBai",1,"Taobao"] </sample>
如果使用了其他类型会报错：

<sample title="" desc="" lang="typescript" hererun="1"> interface namelist {
   [index:number]:string
}

// 类型一致，正确
// var list2:namelist = ["Google","xiaoBai","Taobao"]
// 错误元素 1 不是 string 类型
var list2:namelist = ["John",1,"Bran"] </sample>
执行后报错如下，显示类型不一致：

<pre>test.ts:8:30 - error TS2322: Type 'number' is not assignable to type 'string'.

8 var list2:namelist = [&quot;John&quot;,1,&quot;Bran&quot;]
                               ~

  test.ts:2:4
    2    [index:number]:string
         ~~~~~~~~~~~~~~~~~~~~~
    The expected type comes from this index signature.

Found 1 error.</pre>

== TypeScript ==

<sample title="" desc="" lang="typescript" hererun="1"> interface ages {
   [index:string]:number
}

var agelist:ages;
 // 类型正确
agelist["xiaobai"] = 15

// 类型错误，输出  error TS2322: Type '"google"' is not assignable to type 'number'.
// agelist[2] = "google" </sample>
== 接口继承 ==

接口继承就是说接口可以通过其他接口来扩展自己。

Typescript 允许接口继承多个接口。

继承使用关键字 extends。

单接口继承语法格式：

<pre>Child_interface_name extends super_interface_name</pre>
多接口继承语法格式：

<pre>Child_interface_name extends super_interface1_name, super_interface2_name,…,super_interfaceN_name</pre>
继承的各个接口使用逗号 , 分隔。

=== 单继承实例 ===

== TypeScript ==

<sample title="" desc="" lang="typescript" hererun="1"> interface Person {
   age:number
}

interface Musician extends Person {
   instrument:string
}

var drummer = <Musician>{};
drummer.age = 27
drummer.instrument = "Drums"
console.log("年龄:  "+drummer.age)
console.log("喜欢的乐器:  "+drummer.instrument) </sample>
编译以上代码，得到以下 JavaScript 代码：

== JavaScript ==

<sample title="" desc="" lang="typescript" hererun="1"> var drummer = {};
drummer.age = 27;
drummer.instrument = "Drums";
console.log("年龄:  " + drummer.age);
console.log("喜欢的乐器:  " + drummer.instrument); </sample>
输出结果为：

<pre>年龄:  27
喜欢的乐器:  Drums</pre>
=== 多继承实例 ===

== TypeScript ==

<sample title="" desc="" lang="typescript" hererun="1"> interface IParent1 {
    v1:number
}

interface IParent2 {
    v2:number
}

interface Child extends IParent1, IParent2 { }
var Iobj:Child = { v1:12, v2:23}
console.log("value 1: "+Iobj.v1+" value 2: "+Iobj.v2) </sample>
编译以上代码，得到以下 JavaScript 代码：

== JavaScript ==

<sample title="" desc="" lang="typescript" hererun="1"> var Iobj = { v1: 12, v2: 23 };
console.log("value 1: " + Iobj.v1 + " value 2: " + Iobj.v2); </sample>
输出结果为：

<pre>value 1: 12 value 2: 23</pre>