"Retrieving an element from an array may result in a value of

While going through an array of objects in my Angular component class, I faced a strange issue where the properties kept showing up as undefined. The function responsible for this behavior looks like this:

upload(): void {
    const { fileHandles, relatedThroughID }: { fileHandles: IFileHandle[], relatedThroughID: Guid } = this.form.value;

    const postData: IUploadPost = {
      base64Files: fileHandles.map(fileHandle => ({ data: fileHandle.base64, extension: fileHandle.extension })),
      relatedThroughID: relatedThroughID.toString(),
    };
  }

I was so taken aback by the output displayed while logging results that I had to capture a screenshot - and indeed, the values in the second log statement turned out to be undefined.

https://i.sstatic.net/Uj5fF.png

To add to the confusion, even accessing items by their index revealed properties marked as undefined. This peculiar scenario has left me puzzled and unsure how to rectify it. Can anyone shed light on what might be causing this issue? It's certainly a first for me.

Answer №1

The `fileHandle` variable in your map function is a reference to the array entry, not the actual array entry's `fileHandle` property. Here is the modified code below.

upload(): void {
    const { fileHandles, relatedThroughID }: { fileHandles: IFileHandle[], relatedThroughID: Guid } = this.form.value;

    const postData: IUploadPost = {
      base64Files: fileHandles.map(x => ({ data: x.fileHandle.base64, extension: x.fileHandle.extension })),
      relatedThroughID: relatedThroughID.toString(),
    };
  }

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