How come my push function is not functioning properly on Ionic?

Question

How come my push function is not functioning properly on Ionic?

When working with ionic 3, I encountered an issue with the alert controller while trying to push an element into my array. Despite following the necessary steps of receiving parameters and pushing them, I keep encountering a significant error when attempting to execute my code.

Please forgive me for my poor English proficiency.

CODE

  addPregunta() {
    const prompt = this.alertCtrl.create({
      title: "Login",
      message: "Enter a name for this new album you're looking to add",
      inputs: [
        {
          name: "title",
          placeholder: "Title"
        }
      ],
      buttons: [
        {
          text: "Cancel",
          handler: data => {
            console.log("Cancel clicked");
          }
        },
        {
          text: "Save",
          handler: data => {
            const preObj = {
              type: "radio",
              label: data.title
            };
            this.preguntas.push(preObj);
            this.changeData(data.title);
            this.mermaidStart();
          }
        }
      ]
    });
    prompt.present();
  }

ARRAY

preguntas: object[];

ERROR

https://example.com/image.png

arrays angular typescript ionic3 push

Answer 1

Answer №1

questions: object[]; The questions property is declared but not initialized with a value.

console.log(this.questions) // will be undefined

The issue lies within the save handler:

{
  text: "Save",
  handler: data => {
    const questionObj = {
      type: "radio",
      label: data.title
    };
    this.questions.push(questionObj); // <-- problem line here
    this.changeData(data.title);
    this.mermaidStart();
}

When this.questions.push(questionObj) is first called, this.questions is undefined, so array.push won't work since it's not an array.

You have two options: initialize the questions property as an array or check its value before calling .push.

Option 1

Initialize the property as an array

questions: object[] = [];

Option 2 Check the value in the save handler before pushing.

There are various ways to check or implement an immutable approach

// similar style to your current code
if(this.questions) {
  this.questions.push(questionObj);
} else {
  this.questions = [questionObj];
}

// immutable approach
this.questions = [...this.questions, questionObj]

Answer 2

questions: object[]; The questions property is declared but not initialized with a value.

console.log(this.questions) // will be undefined

The issue lies within the save handler:

{
  text: "Save",
  handler: data => {
    const questionObj = {
      type: "radio",
      label: data.title
    };
    this.questions.push(questionObj); // <-- problem line here
    this.changeData(data.title);
    this.mermaidStart();
}

When this.questions.push(questionObj) is first called, this.questions is undefined, so array.push won't work since it's not an array.

You have two options: initialize the questions property as an array or check its value before calling .push.

Option 1

Initialize the property as an array

questions: object[] = [];

Option 2 Check the value in the save handler before pushing.

There are various ways to check or implement an immutable approach

// similar style to your current code
if(this.questions) {
  this.questions.push(questionObj);
} else {
  this.questions = [questionObj];
}

// immutable approach
this.questions = [...this.questions, questionObj]

Answer 3

Answer №2

The variable was declared as an Array type, but it lacks initialization which causes failure when attempting to push values into it.

Answer 4

The variable was declared as an Array type, but it lacks initialization which causes failure when attempting to push values into it.

How come my push function is not functioning properly on Ionic?

Answer №1

Answer №2

Similar questions

Attempting to create a basic alphabet application using PHP

What steps should I take to create a consistently pristine and efficiently operating Angular 2 setup?

Combining and organizing two sets of objects in Javascript

Is it possible to apply CSS to the alert and confirm functions in Angular?

Production Environment Causing NextJS Website to Malfunction, Development Environment Running Smoothly

Display Angular Material Dialog when TinyMCE is opened in Angular

Create blocks on a painted surface using an assortment

Terminate the loop in a bash script if a certain condition is met

How to manually implement a scrollspy feature in Angular

Is there a way for me to provide a new individual value map as a parameter?

Having trouble retrieving the value in JSON/PHP, even though the value is present and cannot be echoed

Display the elements of an object in a sequential order

Typescript validation of tokens using Azure functions

Discovering the difference between a singular array and an array of arrays

Centralized Vendor Repository for Managing Multiple Angular2 Applications

Obtaining a ParseFile from a JSONArray in Android retrieved from Parse.com CloudCode

The scrolling feature is not working in NativeScript's ScrollView component

The Angular 4 proxy configuration file is not properly directing to the specified target destination; instead, it is redirecting to localhost:4200

Generating Matrix of Indicators

Steps for efficiently reading an array from a file, organizing it, and then saving it to a different file