TypeError: Invalid attempt to spread non-iterable instance

问题

After compiling to android and downloading via Store I get the error:

"TypeError: Invalid attempt to spread non-iterable instance"

But using "react-native run-android" creates no error message therefor I can't find a good way to debug it.

fetch(url)
  .then(response => response.json())
  .then(response => {
    if (this._mounted) {
      // let dataSource = this.state.articlesDataSource.cloneWithRows(response.data || [])
      //var rowCount = dataSource.getRowCount();
      var rowCount = Object.keys(response.data).length;

      if (refresh == true) {
        prevData = {};
      } else {
        prevData = this.state.articlesData;
      }
      if (propSearch == "" || propSearch == null) {
        newArticlesData = [...prevData, ...response.data];
      } else {
        newArticlesData = response.data;
      }
      if (response.meta.next_page != null) {
        var rowCount = true;
      } else {
        var rowCount = Object.keys(newArticlesData).length;
      }
      if (this._mounted) {
        this.setState({
          isLoading: false,
          //articlesDataSource: this.state.articlesDataSource.cloneWithRows(response.data),
          articlesData: newArticlesData,
          nextPage: response.meta.next_page,
          fetchUrl: url,
          rowCount: rowCount
        });
      }
    }
  })
  .catch(error => {
    this.setState({
      errorFound: true,
      errorMassage: error,
      isLoading: false
    }); 
});

Thanks for any help.

回答1:

This is because it is a runtime error, not a "compile time" error.

Is there a line number associated with the error? Based on the question being about the spread operator I'll assume it's this line: newArticlesData=[...prevData,...response.data]. I assume your prevData is iterable, but is your response data? Try newArticlesData=[...prevData, response.data]?

Here's an example of invalid spread operator use:

function trySpread(object) {
  let array;
  try {
    array = [...object];
    console.log('No error', array);
  } catch(error) {
    console.log('error', error);
  }
}

// error
trySpread({});
trySpread({foo: 'bar'});
trySpread(4);

// no error
trySpread([]);
trySpread(['foobar']);
trySpread('foobar');

回答2:

I was getting this crash in release android build only. release ios build and android debug build working perfectly.

After spending a few hours found solutions from the internet.

edit your .babelrc and add following into your plugins

[
      "@babel/plugin-transform-spread",
      {
        "loose": true
      }
    ]

so Here is my .babelrc file

{
  "presets": [
    "module:metro-react-native-babel-preset"
  ],
  "plugins": [
    "syntax-trailing-function-commas",
    "@babel/plugin-transform-flow-strip-types",
    "@babel/plugin-proposal-class-properties",
    "@babel/plugin-transform-regenerator",
    "@babel/plugin-transform-async-to-generator",
    "@babel/plugin-transform-runtime",
    [
      "@babel/plugin-transform-spread",
      {
        "loose": true
      }
    ]
  ],
  "sourceMaps": true
}

I hope this answer helps someone and save few hours :)

回答3:

I removed prevData and replaced it with this.state.articlesData. I also change the logic so at the begining when articlesData is empty, it doesn't merge two objects, instead just uses the response.data.

if(propSearch=="" || propSearch==null && this.state.currentPage!=1 && refresh!=true){
    newData=[...this.state.articlesData,...response.data]
}
else{
    newData=response.data
}

this.state.currentPage!=1 is pretty much the same as oldData != empty

It workes now.

来源：https://stackoverflow.com/questions/53991403/typeerror-invalid-attempt-to-spread-non-iterable-instance

标签

javascript

react-native

react-native-android