[英]Map of generic functions in Typescript
I've got a Message
interface that takes a generic argument T
and sets the value of T
to be the type of an internal property called body
:我有一个Message
的界面,需要一个通用的说法T
,并设置的值T
被称为内部属性的类型body
:
interface Message<T> {
body: T
}
I also have an EventHandler
interface that describes a generic function that takes a Message
as it's sole parameter:我还有一个EventHandler
接口,它描述了一个将Message
作为唯一参数的通用函数:
interface EventHandler<T> {
(event: Message<T>): void
}
Finally, I have an Integration
class that has a subscribe
method and a subscriptions
map that both look like the following:最后,我有一个Integration
类,它有一个subscribe
方法和一个subscriptions
映射,它们都如下所示:
class Integration {
public subscriptions: new Map<string, EventHandler>()
protected subscribe<T>(eventName: string, handler: EventHandler<T>) {
this.subscriptions.set(eventName, handler)
}
}
Ultimately, I want the user to be able to define their own Integration
instances like this:最终,我希望用户能够像这样定义自己的Integration
实例:
interface MyEventProperties {
foo: string
}
class MyIntegration extends Integration {
constructor() {
super()
this.subscribe('My Event Name', this.myEventHandler)
}
myEventHandler(event: Message<MyEventProperties>) {
// do something
}
}
The problem is that this doesn't work.问题是这行不通。 Because I don't know the generic type that ALL EventHandler
functions will be getting I can't define the second generic parameter when instantiating the Map
:因为我不知道所有EventHandler
函数将获得的泛型类型,所以在实例化Map
时我无法定义第二个泛型参数:
class Integration {
public subscriptions: new Map<string, EventHandler>()
// This errors with: Generic type 'EventHandler<T>' requires 1 type argument(s).
protected subscribe<T>(eventName: string, handler: EventHandler<T>) {
this.subscriptions.set(eventName, handler)
}
}
My question is, am I approaching this problem incorrectly or am I missing something more obvious?我的问题是,我是否错误地处理了这个问题,还是遗漏了一些更明显的东西?
The simple solution is to use unknown
as the generic parameter in the map.简单的解决方案是使用unknown
作为地图中的通用参数。 The below solution will work:以下解决方案将起作用:
interface Message<T> {
body: T
}
interface EventHandler<T> {
(event: Message<T>): void
}
class Integration {
public subscriptions = new Map<string, EventHandler<unknown>>()
protected subscribe<T>(eventName: string, handler: EventHandler<T>) {
this.subscriptions.set(eventName, handler)
}
public publishEvent<T>(eventName: string, msg: Message<T>) {
(this.subscriptions.get(eventName) as EventHandler<T>)(msg);
}
}
interface MyEventProperties { foo: string }
class MyIntegration extends Integration {
constructor() {
super()
this.subscribe('My Event Name', this.myEventHandler)
this.subscribe('My Event Name Mistaken', this.myEventHandler) // no relation between name and event
}
myEventHandler(event: Message<MyEventProperties>) {
// do something
}
}
The problem though is there is no relation between the event name and the type of the event.但问题是事件名称和事件类型之间没有关系。 This may be a problem both when subscribing (as highlighted above) but also when emitting the event (the message body would not be checked against the expected message type)这可能是订阅时(如上突出显示)和发出事件时(不会根据预期的消息类型检查消息正文)时出现的问题
I would suggest adding an mapping type between event type and name:我建议在事件类型和名称之间添加一个映射类型:
interface Message<T> {
body: T
}
interface EventHandler<T> {
(event: Message<T>): void
}
class Integration<TEvents> {
public subscriptions = new Map<PropertyKey, EventHandler<unknown>>()
protected subscribe<K extends keyof TEvents>(eventName: K, handler: EventHandler<TEvents[K]>) {
this.subscriptions.set(eventName, handler)
}
public publishEvent<K extends keyof TEvents>(eventName: K, msg: Message<TEvents[K]>) {
(this.subscriptions.get(eventName) as EventHandler<TEvents[K]>)(msg);
}
}
interface MyEventProperties { foo: string }
class MyIntegration extends Integration<{
'My Event Name': MyEventProperties
}> {
constructor() {
super()
this.subscribe('My Event Name', this.myEventHandler)
this.subscribe('My Event Name Mistaken', this.myEventHandler) // error now
this.subscribe('My Event Name', (e: Message<string>) => { }) // error, type of body not ok
}
myEventHandler(event: Message<MyEventProperties>) {
// do something
}
}
let m = new MyIntegration();
m.publishEvent("My Event Name", 0) // error body not ok
m.publishEvent("My Event Name M") // error mistaken name
m.publishEvent("My Event Name", {
body: { foo: ""}
}) // ok message and body correct
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