[英]In TypeScript how do I declare an array of functions that accept a string and return a string?
UPDATE - the context of this question was pre-TypeScript 1.4. 更新 - 此问题的上下文是预先TypeScript 1.4。 Since that version, my first guess has been supported by the language.
从那个版本开始,我的第一个猜测得到了语言的支持。 See the update to the answer.
请参阅答案的更新。
I can declare f
to be a function that accepts a string and returns a string: 我可以声明
f
是一个接受字符串并返回一个字符串的函数:
var f : (string) => string
And I can declare g
to be an array of string: 我可以声明
g
是一个字符串数组:
var g : string[]
How can I declare h
to be an array of "function that accepts a string and returns a string"? 如何将
h
声明为“接受字符串并返回字符串的函数”的数组?
My first guess: 我的第一个猜测:
var h : ((string) => string)[]
That seems to be a syntax error. 这似乎是一个语法错误。 If I take away the extra parentheses then it's a function from string to array of string.
如果我拿掉额外的括号,那么它是一个从字符串到字符串数组的函数。
I figured it out. 我想到了。 The problem is that the
=>
for a function type literal is itself merely syntactic sugar and doesn't want to compose with []
. 问题是函数类型文字的
=>
本身只是语法糖而不想用[]
组成。
As the spec says: 正如规范所说:
A function type literal of the form
表单的函数类型文字
( ParamList ) => ReturnType
(ParamList)=> ReturnType
is exactly equivalent to the object type literal
完全等同于对象类型文字
{ ( ParamList ) : ReturnType }
{(ParamList):ReturnType}
So what I want is: 所以我想要的是:
var h : { (s: string): string; }[]
Complete example: 完整的例子:
var f : (string) => string
f = x => '(' + x + ')';
var h : { (s: string): string; }[]
h = [];
h.push(f);
Update : 更新 :
Judging from this changeset parentheses will be allowed in type declarations in 1.4, so the "first guess" in the question will also be correct: 从这个变更集判断,在1.4中的类型声明中将允许使用括号,因此问题中的“第一个猜测”也是正确的:
var h: ((string) => string)[]
Further Update It is in 1.4! 进一步更新它在1.4!
Based on your research I wrote a little class PlanetGreeter/SayHello:` 根据你的研究,我写了一个小类PlanetGreeter / SayHello:`
/* PlanetGreeter */
class PlanetGreeter {
hello : { () : void; } [] = [];
planet_1 : string = "World";
planet_2 : string = "Mars";
planet_3 : string = "Venus";
planet_4 : string = "Uranus";
planet_5 : string = "Pluto";
constructor() {
this.hello.push( () => { this.greet(this.planet_1); } );
this.hello.push( () => { this.greet(this.planet_2); } );
this.hello.push( () => { this.greet(this.planet_3); } );
this.hello.push( () => { this.greet(this.planet_4); } );
this.hello.push( () => { this.greet(this.planet_5); } );
}
greet(a: string): void { alert("Hello " + a); }
greetRandomPlanet():void {
this.hello [ Math.floor( 5 * Math.random() ) ] ();
}
}
new PlanetGreeter().greetRandomPlanet();
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