[英]Interface function with some properties (TypeScript)?
How can I use following interface?如何使用以下界面?
interface Something {
(n: number): void,
description: string
}
I try writing following.我试着写以下。
var sth: Something = {
description: "Description"
}
sth = (n: number) => {
console.log("Something");
}
or或者
var sth: Something = {
(n: number) => {
console.log("Something");
},
description: "Description"
}
But they both give errors.但他们都给出了错误。
You cannot directly create an object which is both a function and has other properties.您不能直接创建既是函数又具有其他属性的对象。 You have to do it in two steps, first create a function, then assign it another prop, then assign the result to a variable of your interface:
您必须分两步完成,首先创建一个函数,然后为其分配另一个 prop,然后将结果分配给您界面的一个变量:
interface Something {
(n: number): void;
description: string;
}
function fn(n: number) {}
fn.description = 'foo';
const h: Something = fn;
You can do it in one of few ways.您可以通过以下几种方式之一来完成。 Each fits slightly odd with functions with properties but all are viable, depending on the use case:
每个都适合具有属性的函数,但都是可行的,具体取决于用例:
There is no syntax for creating a function with a property.没有用于创建具有属性的函数的语法。 You have to do both separately:
你必须分开做:
var sth: Something = ((n: number) => {
console.log(n + 2);
}) as Something;
sth.description = "Description";
The as Something
assertion is needed here to tell the compiler to treat the function as Something
, otherwise you cannot add the description
.这里需要
as Something
断言来告诉编译器将函数视为Something
,否则您无法添加description
。
Object.assign()
This allows declaring everything at once:这允许一次声明所有内容:
var sth: Something = Object.assign(
(n: number) => {
console.log(n + 2);
},
{ description: "Description"}
);
Object.assign
is typed to return any
so the type declaration sth: Something
makes sure it is treated as the correct object afterwards. Object.assign
被输入为返回any
所以类型声明sth: Something
确保之后它被视为正确的对象。
Object.defineProperty()
Another way to create an object and add a property.另一种创建对象并添加属性的方法。 It allows more control over the property, like making it non-writable, if needed.
如果需要,它允许对属性进行更多控制,例如使其不可写。
var sth: Something = Object.defineProperty(
(n: number) => {
console.log(n + 2);
},
"description",
{ value: "Description"}
) as Something;
The as Something
assertion is needed because Object.defineProperty()
is typed to return the same as the first argument.因为
Object.defineProperty()
的类型与第一个参数相同,所以需要as Something
断言。 So it returns (n: number) => void
.所以它返回
(n: number) => void
。
Object.defineProperties()
Very similar to Object.defineProperty()
but allows multiple properties to be configured at once.与
Object.defineProperty()
非常相似,但允许一次配置多个属性。
var sth: Something = Object.defineProperties(
(n: number) => {
console.log(n + 2);
},
{
description: { value: "Description" }
}
) as Something;
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