如何在省略一些其他可选参数的同时在TypeScript中传递可选参数？

Question

鉴于以下签名:

export interface INotificationService {
    error(message: string, title?: string, autoHideAfter?: number);
}

如何调用函数error()而不指定title参数,但将autoHideAfter设置为1000？

Answer 1

如文档中所述,使用undefined:

export interface INotificationService {
    error(message: string, title?: string, autoHideAfter? : number);
}

class X {
    error(message: string, title?: string, autoHideAfter?: number) {
        console.log(message, title, autoHideAfter);
    }
}

new X().error("hi there", undefined, 1000);

游乐场链接.

Answer 2

不幸的是,在TypeScript中没有这样的东西(更多细节在这里:https://github.com/Microsoft/TypeScript/issues/467)

但是为了解决这个问题,你可以将你的参数改为接口:

export interface IErrorParams {
  message: string;
  title?: string;
  autoHideAfter?: number;
}

export interface INotificationService {
  error(params: IErrorParams);
}

//then to call it:
error({message: 'msg', autoHideAfter: 42});

Answer 3

您可以使用可选变量,?或者如果您有多个可选变量...,例如:

function details(name: string, country="CA", address?: string, ...hobbies: string) {
    // ...
}

在上面:

• name 是必须的
• country 是必需的,并具有默认值
• address 是可选的
• hobbies 是一组可选参数

Answer 4

另一种方法是：

error(message: string, options?: {title?: string, autoHideAfter?: number});

因此，当您想省略title参数时，只需发送如下数据：

error('the message', { autoHideAfter: 1 })

我宁愿使用此选项，因为它允许我添加更多参数而不必发送其他参数。

Answer 5

这与@Brocco的答案几乎相同,但略有不同:只传递对象中的可选参数.(并且还使params对象可选).

它最终有点像Python的**kwargs,但并不完全如此.

export interface IErrorParams {
  title?: string;
  autoHideAfter?: number;
}

export interface INotificationService {
  // make params optional so you don't have to pass in an empty object
  // in the case that you don't want any extra params
  error(message: string, params?: IErrorParams);
}

// all of these will work as expected
error('A message with some params but not others:', {autoHideAfter: 42});
error('Another message with some params but not others:', {title: 'StackOverflow'});
error('A message with all params:', {title: 'StackOverflow', autoHideAfter: 42});
error('A message with all params, in a different order:', {autoHideAfter: 42, title: 'StackOverflow'});
error('A message with no params at all:');

Answer 6

您可以在接口上指定多个方法签名,然后在类方法上有多个方法重载:

interface INotificationService {
    error(message: string, title?: string, autoHideAfter?: number);
    error(message: string, autoHideAfter: number);
}

class MyNotificationService implements INotificationService {
    error(message: string, title?: string, autoHideAfter?: number);
    error(message: string, autoHideAfter?: number);
    error(message: string, param1?: (string|number), param2?: number) {
        var autoHideAfter: number,
            title: string;

        // example of mapping the parameters
        if (param2 != null) {
            autoHideAfter = param2;
            title = <string> param1;
        }
        else if (param1 != null) {
            if (typeof param1 === "string") {
                title = param1;
            }
            else {
                autoHideAfter = param1;
            }
        }

        // use message, autoHideAfter, and title here
    }
}

现在所有这些都可行:

var service: INotificationService = new MyNotificationService();
service.error("My message");
service.error("My message", 1000);
service.error("My message", "My title");
service.error("My message", "My title", 1000);

...并且error方法INotificationService将具有以下选项:

操场