自学鸿蒙HarmonyOS的ArkTS语言＜十＞@BuilderParam装饰器

作用：当子组件多处使用时，给某处的子组件添加特定功能

一、初始化

1、只能被@Builder装饰的方法初始化
2、使用所属自定义组件的@builder方法初始化
3、使用父组件的@builder方法初始化 - 把父组件的@builder传过去，参数名和子组件的@builderParam同名

@Component struct Child {   @Builder childBuilder() {}   @BuilderParam childBuilderParam: () => void = this.childBuilder // 必须用childBuilder初始化下，否则预览出不来    build() {     Column() {       Text('我是子组件')         .fontColor(Color.White)       this.childBuilderParam()     }   } }  @Entry @Component struct Index7 {    @Builder parentBuilder() {     Text('我是父组件定制的的 builder')    }    build() {     Column() {       Row() {         Child({childBuilderParam: this.parentBuilder}) // 添加独特功能       }       .padding(10)       .backgroundColor(Color.Brown)        Row() {         Child()       }       .padding(10)       .backgroundColor(Color.Green)      }   } } 

二、this指向

@Component struct Child1 {   label: string = '我是子组件的label'   @Builder childBuilder() {}   @BuilderParam childBuilderParam: () => void = this.childBuilder   @BuilderParam childChangeThisBuilderParam: () => void = this.childBuilder    build() {     Column() {       this.childBuilderParam()       this.childChangeThisBuilderParam()     }   } }  @Entry @Component struct Index7_1 {   label: string = '我是父组件的label'    @Builder parentBuilder() {     Text(this.label)    }    build() {     Column() {       this.parentBuilder() // this指向父组件         Child1({         childBuilderParam: this.parentBuilder, // this.parentBuilder传入到child中指向child         childChangeThisBuilderParam: (): void => this.parentBuilder(), // 箭头函数的this指向宿主对象，即父组件       })      }   } } 

三、带参数

class Tmp {   label: string = '' } // 全局builder @Builder function globalBuilder($$: Tmp) {   Text($$.label) }  // Child1中 ... // 有参数 @BuilderParam childHasParamsBuilderParam: ($$: Tmp) => void = globalBuilder build() {   Column() { 	  ... 	  this.childHasParamsBuilderParam({label: '我是一个有参数的BuilderParam'})   } } // 父组件中 ... Child1({   ...   childHasParamsBuilderParam: globalBuilder }) 

四、尾随闭包的形式

@Component struct Child2 {   @Builder childBuilder() {}   // 尾随闭包的形式传入时子组件内只能有一个BuilderParam   @BuilderParam childBuilderParam: () => void = this.childBuilder    build() {     Column() {       Text('我是子组件2')       this.childBuilderParam()     }     .margin({top: 30})   } } // 父组件中 ... Child2() {    Column() {      globalBuilder({label: '我是通过尾随闭包传入的'})    } } 

注意：
尾随闭包的形式子组件内只能有一个 @BuilderParam