The property 'unshift' is not defined and cannot be read

I encountered an issue while trying to add a new book to my books array and received an error message. https://i.sstatic.net/PaUA8.png

This pertains to the book-edit.component.ts

When initializing:
  Upon initializing, I subscribed to changes in authors through the authors service. This is triggered when there are changes made to the authors list.
    this.authors = authors;
  
  I also called for the retrieval of authors using the getAuthors() method provided by the authors service.

  The bookForm instance was created with pre-filled values for various form controls such as id, title, author, description, publishYear, and image.

In the onSubmit() method: Upon form submission, the values entered in the form are captured and assigned to respective properties of a book object. const book = { id: this.bookForm.value.id, title: this.bookForm.value.title, author: this.bookForm.value.author, description: this.bookForm.value.description, publishYear: this.bookForm.value.publishYear, image: this.bookForm.value.image }; The addBook() method from the booksService is then called with the newly created book object passed as an argument.

Function from the booksService.ts:

The addBook(book: Book) method within the books service is responsible for adding a new book into the beginning of the books array. It notifies subscribers about the change in the books array by emitting the updated array via the booksChanged subject.

Answer №1

It appears from the error log that this.books has not been initialized. To address this issue, could you please initialize the books variable in bookservice.ts to an empty array like books = []

addBook(book: Book) {
    this.books.unshift(book);
    this.booksChanged.next(this.books);
  }

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