ValidateForm emitter.on emitter.off 报错

Question

Answer 1

张轩 2020-10-01 22:07:08

同学你好 请问你的 callback 是怎样定义的，请把代码贴一下，mitt 的定义文件在我当时录课之后有了一小部分的更新，有可能会出现类型错误，可以参考这个常见问题 http://coding.imooc.com/learn/questiondetail/206736.html

• Linx #1

  emitter报错：
  No overload matches this call.
    Overload 1 of 2, '(type: "*", handler: WildcardHandler): void', gave the following error.
      Argument of type '"form-item-created"' is not assignable to parameter of type '"*"'.
    Overload 2 of 2, '(type: string | symbol, handler: Handler<ValidateFunc>): void', gave the following error.
      Argument of type '(func: ValidateFunc) => void' is not assignable to parameter of type 'Handler<ValidateFunc>'.
        Types of parameters 'func' and 'event' are incompatible.
          Type 'ValidateFunc | undefined' is not assignable to type 'ValidateFunc'.
            Type 'undefined' is not assignable to type 'ValidateFunc'.Vetur(2769)
  
  代码如下：
  const callback = (func: ValidateFunc) => {
        funcArr.push(func)
      }
      emitter.on('form-item-created', callback)
      onUnmounted(() => {
        emitter.off('form-item-created', callback)
      })
  
  如果写成const callback = (func: any) ，就不会报错，为什么这个类型推断会产生错误？我看了emitter的EventType是any，没搞明白

• 慕尼黑6512596 #2

  求解
  const callback = (func?: ValidateFunc) => {
        funcArr.push(func)
      }
  也会爆错

• EditYJ 回复 慕尼黑6512596 #3

  const childCallback: Handler<ValidateFunc> = (func) => {
        if (func) {
          validateFuncList.push(func);
        }
      };
      emitter.on('form-item-created', childCallback);

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