React array of refs

问题

i have read in a post on Stackoverflow question about refs

that we can use something like the following code to assign an array of refs to different inputs like this:

<Progressbar completed={25} id="Progress1" ref={(input) => {this.Progress[0] = input }}/>

<Progressbar completed={50} id="Progress2" ref={(input) => {this.Progress[1] = input }}/>

<Progressbar completed={75} id="Progress3" ref={(input) => {this.Progress[2] = input }}/>

but when i try it, it returns this error:

Uncaught TypeError: Cannot set property '0' of undefined

and it doesn't work, am I missing something?

回答1:

Create the array in you constructor, like:

constructor(){
  super()

  this.Progress = []
}

回答2:

Progress array is not initialized, initialize it in constructor..

来源：https://stackoverflow.com/questions/45326832/react-array-of-refs