[英]Typescript: assign a readonly attribute in a function inside the constructor
我有一个具有只读属性的类,该类在constructor
function
内部的function
定义,编译器发出错误,我不知道如何解决:
class TEST {
public readonly desc: string;
constructor() {
const compute = () => {
this.desc = "description"
};
}
}
编译器说: "Cannot assign to "desc" because it is a readonly property"
但我认为在构造函数内部分配该属性将避免此类错误。 有可能还是必须更改实施方式?
您将需要类型断言来解决它,这是使用映射类型从类型中删除readonly
的最安全的方法:
type Mutable<T> = {
-readonly [P in keyof T]: T[P];
};
class TEST {
public readonly desc!: string;
constructor() {
const compute = () => {
(this as Mutable<TEST>).desc = "description"
};
}
}
readonly
是一个相当弱的修饰符,因此,如果您不介意this
作为参数传递,则可以避免断言:
class TEST {
public readonly desc!: string;
constructor() {
const compute = (target: Mutable<TEST>) => {
target.desc = "description"
};
compute(this)// works fine and not just because we are in teh constructor
}
}
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