怎么把子组件的方法暴露给父组件调用？

@Entry  
@Component  
struct Index {  
  build() {  
    Column() {  
      TitleBar({  
        submit:()=>{  
          console.log("请在此处执行提交操作")  
        }  
      })  
    }  
  }  
}  
  
@Component  
export struct TitleBar {  
  submit?: () => void  
  
  build() {  
    Row(){  
      Text('cunstom Title')  
        .layoutWeight(1)  
        .textAlign(TextAlign.Center)  
      Button('提交')  
        .width(80)  
        .onClick(()=>{  
          if(this.submit){  
            this.submit()  
          }  
        })  
    }  
    .justifyContent(FlexAlign.SpaceBetween)  
    .height(56)  
  }  
}