javascript - Vue : How to set data from within an "inner" function?

Question

我正在使用 Vue 和 Axios 来显示进度条。 uploadProgress 是我的 Vue 实例中的数据键。当我尝试使用内部函数设置它时，它只是说它未定义。这是我的代码的简化版本:

someVueMethod() {
  this.uploadProgress = 0 // this works

  let config = { 
    onUploadProgress(progress) {
      // this doesn't work, error says uploadProgress is undefined
      this.uploadProgress += progress.loaded / progress.total
    }
  }
  axios.put(url, file, config).then(res => {
    // handle the response
  })
}

如何在该内部函数中设置uploadProgress？

Answer 1

您已将 uploadProgress 添加到函数 someVueMethod 的上下文中，但尝试在函数 onUploadProgress 的上下文中访问它。您需要像这样使用原始上下文。

someVueMethod() {
  var self = this; //store the context of someVueMethod
  this.uploadProgress = 0 // this works

  let config = { 
    onUploadProgress(progress) {
      // use the original context using self
      self.uploadProgress += progress.loaded / progress.total
    }
  }
  axios.put(url, file, config).then(res => {
    // handle the response
  })
}