[英]Conditional method parameters based on Generic type
I am in the process of writing a new TypeScript class which takes a generic value that will be used as the input to a function. 我正在编写一个新的TypeScript类,该类具有一个将用作函数输入的通用值。 If a value isn't given, than the function should not take any inputs.
如果未提供值,则该函数不应接受任何输入。
Ideally the class would be overloaded like this. 理想情况下,此类将像这样重载。
class Emitter<T = void> {
public activate(): void // When T is void
public activate(arg: T): void // When T isn't void
public activate(arg?: T) { /* ... */ }
}
Having the method be a function property works in theory but requires a @ts-ignore
on the method's implementation. 使该方法成为函数属性在理论上是
@ts-ignore
但是需要对该方法的实现使用@ts-ignore
。
type OneArgFn<T> = T extends void
? () => void
: (arg: T) => void
interface Emitter<T> {
readonly activate: OneArgFn<T>
}
Another possibility is to export a different constructor when a Generic is provided or not, such as the following 另一种可能性是在是否提供泛型时导出不同的构造函数,例如以下内容
interface EmitterNoArg extends Emitter {
activate: () => true
}
interface EmitterOneArg<T> extends Emitter<T> {
activate: (arg: T) => void
}
interface EmitterConstructor {
new(): Emitter
new(): EmitterNoArg
new<T>(): EmitterOneArg<T>
}
but then to export it the unknown
keyword is required. 但要导出该关键字,则需要
unknown
关键字。
export default Emitter as unknown as EmitterConstructor
These, do not seem to be optimal. 这些似乎不是最佳的。 Is there a proper way to have conditional arguments based on the Generic's type?
是否有适当的方法可以基于泛型的类型获取条件参数? I would think TypeScript's new conditional types would solve this issue.
我认为TypeScript的新条件类型将解决此问题。
One way to do it would be using tuples in rest parameters in a separate public signature: 一种方法是在单独的公共签名中的rest参数中使用元组:
type OneArgFn<T> = T extends void
? () => void
: (arg: T) => void
class Emitter<T = void> {
public activate(...a: Parameters<OneArgFn<T>>): void
public activate(arg?: T) { /* ... */ }
}
new Emitter().activate();
new Emitter<string>().activate("") // in 3.4 argument names are preserved
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