[英]Typescript Union Type and Interface
I am new in typescript, i don't understand why interface is not declare in object when i call an array or function property. 我是打字稿的新手,我不明白为什么当我调用数组或函数属性时,接口没有在对象中声明。 if i call it form any object then array or function property getting error. 如果我将其称为任何对象,则数组或函数属性会出错。
where i'm use address property as string then i declare interface in makeNewEmployee object then there are no error. 我在其中使用地址属性作为字符串,然后在makeNewEmployee对象中声明接口,然后没有错误。 i'm little bit confused about that. 我对此有些困惑。
here is my code 这是我的代码
interface makeAnything{
user:string;
address:string| string[]| (()=>string);
}
/// address as string
let makeNewEmployee:makeAnything = {
user:"Mirajehossain",
address:"Dhaka,Bangladesh"
};
console.log(makeNewEmployee.address);
here i'm use makeAnything interface in my makeNewEmployee object and declare address property as function , why i get error in console? 在这里,我在makeNewEmployee对象中使用makeAnything接口,并将address属性声明为function,为什么在控制台中出现错误?
///address as function
let makeSingleEmployee:makeAnything = {
user:'Miraje hossain',
address:():any=>{
return{
addr:"road 4,house 3",
phone:18406277
}
}
};
console.log(makeSingleEmployee.address()); ///getting error
You can use type guards to help the compiler know that address
is a function. 您可以使用类型保护来帮助编译器知道address
是一个函数。 See type guards . 请参阅防护罩 。
Examples: 例子:
// string or string[] cannot be instances of Function. So the compiler infers that `address` must be (()=>string)
if (makeSingleEmployee.address instanceof Function) {
console.log(makeSingleEmployee.address());
}
// typeof makeSingleEmployee.address will be "function" when address is a function
if (typeof makeSingleEmployee.address != "string" && typeof makeSingleEmployee.address != "object" ) {
console.log(makeSingleEmployee.address());
}
Or if you know for sure address
is a function, you can cast it to any
: 或者,如果您确定address
是一个函数,则可以将其强制转换为any
:
console.log((makeSingleEmployee as any).address());
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