[Tutorial]: Ionic App Development: Building the buisness app part 4

Image Source

Repository: Ionic Framework Github Repository

Software Requirements: Visual Studio Code(Or any preferred editor)
A browser(Preferably Chrome)

What you will learn:

• Passing Data through pages using Events and modals

• Making Dynamic Angular components

• Styling and design methods

Difficulty: Intermediate

Tutorial
In the last post we did quite a lot for our development by theming our app and adding a few lists and functionalities. Today we will be binding more elements to our inputs using Angular and learning how to pass useful data through pages. In ionic they are four major methods of passing data through pages. They are:

• Pushing using navCtrl
• Using Modals
• Using Providers
• and using events

In this tutorial we will be using two which are the events and modals.
Modals are usually used for editing components. For example if you're on a list and want to edit the content of one of the list items, a modal would be the best way to pass data to the editing page and pass the edited data back to your original page.
Note: Immediately the modal is dismissed, the modal is destroyed.

Before we get into that lets go to our start page and bind the balance to our updated balance using angular.
Ionic has angular inbuilt so unlike a normal angular project you can simply define the variables in the .ts file for that page and directly refer to it using the ngModel directive.
Our code should look like this
home.ts

import { Component } from '@angular/core';
import { NavController, Events } from 'ionic-angular';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  public balance: number= 0;//Simply define a preset value for your balance using typescript

home.html

<ion-header>
  <ion-toolbar>
    <ion-title>
      <div class="pageheader">The Buisness App</div>
    </ion-title>
  </ion-toolbar>
</ion-header>
<ion-content padding:10px class="background">
  
  <ion-card>
    <ion-card-header>
      <div text-center class="balanceheading">
        <h1>
          BALANCE
        </h1>
      </div>
    </ion-card-header>
    <hr>
    <ion-card-content>
      <div text-center class="balancecontent">
        Your current account balance is
      </div><br>
      <div text-center class="balance_value">
        {{ balance | currency : "N" }}//Simply refer to your variable like this using our angular directive.
      </div>

So now we can progress to our products page. With the knowledge of styling from the last tutorial you should understand the styling the .html file below.
products.html

<ion-header>

  <ion-navbar>
    <ion-title>Products</ion-title>
  </ion-navbar>

</ion-header>
<ion-content  class="background" padding:10px>
  
    <ion-card>
        <ion-card-header>
          Manage your products
        </ion-card-header>
        <ion-card-content>
            <p>The total selling price of your good is:<br> {{ balance | currency : "N" }}</p>
          Here you can manage all the products in your store and keep accurate count of everything bought to maximize profits
        </ion-card-content>
      </ion-card>
  <button ion-button full (click)="createNewProduct()">
    Add a new product
  </button>    
  <ion-card>
    <ion-list inset>
      <ion-list-header>
      Your products
      </ion-list-header>
        <button ion-item *ngFor="let item of items" (click)="itemSelected(item)">
            <ion-icon name="{{ item.type }}"> {{ item.name }}</ion-icon><div text-right>{{ item.sellingprice | currency : "N" }}</div>
          <hr>  
        </button>
    </ion-list>
  </ion-card>  
</ion-content>

But what i mainly want you to take note of is the button with *ngFor. This is the method used for iterating through arrays and even for creating infinite content read from a server. The *ngFor directive iterates through an array and repeats the .html tag its within for every element in the array. In infinite scroll media a server just keep serving data into this array which will continuously displays this in the view.
So with that we can see form this line *ngFor="let item of items" that the process iterates through an array called items which is not yet available in our .ts file. So we will have to head there and create this.

products.ts

import { Component } from '@angular/core';
import { IonicPage, NavController, NavParams, ModalController, Events } from 'ionic-angular';
import { NewproductPage } from '../newproduct/newproduct';

@IonicPage()
@Component({
  selector: 'page-products',
  templateUrl: 'products.html',
})
export class ProductsPage {
  public items:any=[{name: "Hello", type="cafe", price="500"},{name: "Hello", type="cafe", price="500"}]//Use this simple example to test and see that this is working.

Another thing youll notice in the .html file is that we added a <button (click)="createNewProduct"> which calls a function called create new product. This is where the modal comes in. We are going to create a modal which will add to this items array. So lets get on to that.
First you create a new page called the newproductPage using

ionic g page newproduct

Then import it into your app.module.ts as taught in the last tutorial

Beneath your constructor add this
product.ts

createNewProduct(){
    let newItemModal = this.modalCtrl.create(NewproductPage);//This will create new modal with the content of the new product page.
    newItemModal.present();//This will present the modal to the viewer

So this will display a blank page for now because we havent added any .html content.
Head to your newproductPage.html and style it using this template to gather input

<ion-header>

  <ion-navbar>
    <ion-title>Add a New Product</ion-title>
  </ion-navbar>

</ion-header>
<ion-content class="background" padding>
     <ion-list margin:50px>
        <ion-list-header primary>What is the name of your product</ion-list-header>
        <ion-item>
          <ion-label floating>Product Name</ion-label>
          <ion-input [(ngModel)]="product.name" type="text"></ion-input>//Bind all values to their variables
        </ion-item>
      </ion-list>
      <br>
      <hr>
      <ion-list>
        <ion-list-header>
          What type of product 
        </ion-list-header>
          <ion-item>
            <ion-label>Product type</ion-label>
            <ion-select [(ngModel)]="product.type">
              <ion-option value="cafe">Beverage</ion-option>
              <ion-option value="eye">Cosmetic</ion-option>
              <ion-option value="phone-potrait">Gadget</ion-option>
              <ion-option value="woman">Clothing</ion-option>
              <ion-option value="watch">Clothing accesory</ion-option>
              <ion-option value="square">Not in options</ion-option>
            </ion-select>
          </ion-item>
        </ion-list>
        <br>
        <hr>
        <ion-list>
          <ion-list-header>What is the Cost Price of your product?</ion-list-header>
          <p>How much did you buy the product?</p>
          <ion-item>
            <ion-label floating>Product Price</ion-label>
            <ion-input type="number" [(ngModel)]="product.costprice"></ion-input>
          </ion-item>
      </ion-list>
      <br>
      <hr>
        <ion-list>
            <ion-list-header>What is the Selling Price of your product?</ion-list-header>
            <p>How much do you sell the product?</p>
            <ion-item>
              <ion-label floating>Product Price</ion-label>
              <ion-input type="number" [(ngModel)]="product.sellingprice"></ion-input>
            </ion-item>
        </ion-list>

        <button ion-button light (click)="savedata()">
          Save
        </button>
        
</ion-content>

If you look through this html content you would see that we binded many angular directives to variables that dont exist yet. So well head to the newproductpage.ts and add the variables.

newproductpage.ts

@IonicPage()
@Component({
  selector: 'page-newproduct',
  templateUrl: 'newproduct.html',
})
export class NewproductPage {
  product: any={name: "",type: "",costprice: 0,sellingprice: 0}//These are the values we want to collect from this page

So now when you save you should see all the nice content on the page.
When the user inputs data he would want to save this data and you would like this data to add to the items in the products page. That would be done with the saveData() function that we bound to the save button in our html file.
To dismiss a modal ionic uses a different import from ionic-angular called the ViewController
So go to your newproductpage.ts and import ViewController and add it to your controller like this.

import { Component } from '@angular/core';
import { IonicPage, NavController, NavParams, ViewController } from 'ionic-angular';

@IonicPage()
@Component({
  selector: 'page-newproduct',
  templateUrl: 'newproduct.html',
})
export class NewproductPage {
  product: any={name: "",type: "",costprice: 0,sellingprice: 0}

  constructor(public navCtrl: NavController, public navParams: NavParams, public viewCtrl: ViewController) {
  }//This makes the ViewController usable in this page.

So now that we've injected the viewcontroller its time to use it in our saveData() function and pass data using it.
Create the new function beneath your controller like this.

savedata(){
    if(this.product){
      let data = this.product;
      this.viewCtrl.dismiss(data); //This is the function that dismisses the modal and passes the data we've collected from the input to the products page.
    } else {
      this.viewCtrl.dismiss();
      console.log("No data input");
      }//We do this so that if no data isnt added it wont add a blank value to our products page
  }

The final thing we'll be doing today is collecting the data we've collected from this list and adding it to the items array in our products page.
To do this we add something to the function that create the modal. The function is called onDidDismiss and it is inbuilt into ionic.
Add this to your createnewproduct function.

 createNewProduct(){
    let newItemModal = this.modalCtrl.create(NewproductPage);
    newItemModal.onDidDismiss((data) => {
      if(data){//This checks if data is actually collected so we wont log blank values to the items array
        this.items.unshift(data);//This adds the data collected to the array
        this.balance = this.balance + parseInt(data.sellingprice);//This updates our balance record
        let balance = this.balance;
        let items = this.items
        this.events.publish('balance',balance,items);//This creates a new event.
      
      }
      else {
          console.log('no data received')
        }
      
    })
    newItemModal.present(); 
  }

We see that all the data we've collected so you can save and test. In the next tutorial we will be dealing with events that we added to the function and explaining its use and how it will be used in this application.

You can find my code in Github