[英]proper way to override function with different param types in TypeScript
TL;DR; TL; DR; my
formatAPI
function below is very much not the TYpeScript way of overriding a function... 我下面的
formatAPI
函数几乎不是 TYpeScript覆盖函数的方式...
I've got a function that might be called either of following four ways in JavaScript: 我有一个可以在JavaScript中通过以下四种方式之一调用的函数:
jsf.format("format", function(){ return ... }); // string, function
jsf.format("format"); // string
jsf.format({
"format1": function(){ return ... },
"format2": function(){ return ... }
}); // map[string:function]
jsf.format(); // no params
Each signature executes different logic beneath. 每个签名执行下面的不同逻辑。 CUrrently I've got the following:
目前,我有以下内容:
function formatAPI(name: string, callback?: Function): any {
if (callback) {
registry.register(name, callback);
} else if (typeof name === 'object') {
registry.registerMany(name);
} else if (name) {
return registry.get(name);
} else {
return registry.list();
}
}
but it's inconsistent - eg second parameter is string
. 但是不一致-例如,第二个参数是
string
。 When I change it to string|Object
than it fails on my logic ( registry.register(name, callback);
- name
here has to be a string and string|Object
is not assignable to string). 当我将其更改为
string|Object
,它在我的逻辑上就失败了( registry.register(name, callback);
-这里的name
必须是字符串,并且string|Object
无法分配给string)。 I'm trying to find a clear and extensible solution (to be able to add more variations if I need to, in the future), I try to adapt another question but I fail. 我试图找到一个清晰且可扩展的解决方案(以便将来能够根据需要添加更多的变体),但是我尝试适应另一个问题,但失败了。
I would appreciate help and/or advise on how should I declare all possible signatures for this function AND the function body. 我将不胜感激,并且/或者建议我应该如何声明该函数和函数体的所有可能签名。
It slices! 切成薄片! it dices!
它切成小方块! It makes toast!
它烤面包!
// Signatures
function formatAPI(): string[];
function formatAPI(name: string): string;
function formatAPI(name: string, callback: (arg: string) => void): void;
function formatAPI(map: { [name: string]: () => string }): void;
// Implementation
function formatAPI(nameOrMap?: string | { [name: string]: () => string }, callback?:(arg: string) => void): string | string[] | void {
if (typeof nameOrMap === 'string') {
if (callback) {
return registry.register(nameOrMap, callback);
} else {
return registry.get(nameOrMap);
}
} else if (...) {
// Keep adding checks here
}
}
One thing to note is that the compiler doesn't use the signatures to infer behavior for type guards. 要注意的一件事是,编译器不使用签名来推断类型防护的行为。 This means you should structure your code slightly more conservatively -- here, I put both
string
cases inside the typeof
check. 这意味着您应该更加保守地构造代码-在这里,我将两个
string
放在了typeof
检查中。
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