父组件与子组件如何实现双向绑定？ 难道每次都触发父组件的方法吗

[xxrxd]

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Description

[问题描述：站在其它人的角度尽可能清晰地、简洁地把问题描述清楚]

[Description of the issue]

Environment

• Platform: [开发者工具/iOS/Andriod/Web]
• Platform version: [对应工具或者iOS或者Andriod的版本号]
• Wechat version: [微信版本号]
• wepy-cli version: [wepy-cli -v]
• wepy version: [在package.json里]
• other version: [如果是插件问题，请列出问题插件的版本号]

Reproduce

[如何重现问题]

[How to reproduce the issue]

Observed Results

[实际表现]

[Observed Results]

Expected Results

[期望表现]

[Expected Results]

Relevant Code / Logs

// TODO(you): code or logs here to reproduce the problem
 // 可以使用小程序代码片段功能，方便其它人帮助你定位代码问题
 // 详情可参考这里：https://developers.weixin.qq.com/miniprogram/dev/devtools/minicode.html
 ```