Inner Classes with TypeScript

原文：https://blog.oio.de/2014/03/21/inner-classes-typescript/

b.ts

class Foo {
    sex:string;
    say(){
        new Foo.InnerFoo('aaa').doIt();
    }
}

module Foo {
    export class InnerFoo {
        constructor(name:string){
            console.log(name);
        }
        doIt() {
            console.log('inner class do it.');
        }
    }
}

let a = new Foo.InnerFoo('fly');
let b = new Foo();
b.say();

　　

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In TypeScript, there is no exlicit concept like inner classes.
So what you cannot do in TypeScript is as follows:

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class Foo {   export class InnerFoo {   } }   new Foo.InnerFoo();

You can achieve something similar by merging a class with a module containing the inner class.

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class Foo { }   module Foo {     export class InnerFoo {       doIt(){}     } }   new Foo.InnerFoo();

The merging happens implicitely by using the same name for the class and the module.

Of course you can use the inner class in the outer class:

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class Foo {     doSomethingWithInnerFoo() {         new Foo.InnerFoo().doIt();     } }   module Foo {     export class InnerFoo { doIt(){} } }   new Foo().doSomethingWithInnerFoo();

The only downside here is that the inner class must be exported, so it is always visible to the outside – there are no private inner classes.