在TypeScript中，如何在类构造函数中使用外部函数并从回调中获取值并分配给属性

Question

How can I assign "aaa" to a??I can't write getStr() in this class because it form a library

class a {
    aaa: String
    constructor(aaa) {
        getStr(function(str) {
            // this.aaa = str
        })
    }
}

function getStr(callback) {
    callback("aaa")
}

Answer 1

If you have callback I assume we are talking about async execution. In this case the answer is

You cannot

By definition constructor must return instance of the constructed class. This is important. Not a Promise<MyClass> , not a Promise<void> . Therefore what you are trying to archive is not possible.

Please do not follow the illusion that you can call async function in constructor and it will do the work. It will be finished sometime after constructor code is finished executing, or maybe not - depending on other code that gets executed alongside. This uncertainty - makes this approach extremely dangerous and unpredictable.

What you can do - usually if you need to perform some initialization of the instance that requires async calls - you create a separate init(): promise<void> function that can be correctly called and awaited.