By : shabda

This is next in the series of apps I am building using various mobile technologies. It is the same app as build using Java for Android for calculating the Tax payable (in India). You can get the code for Objective-C, Java-Android, and PhoneGap.

First the impressions

Phonegap was the easiest to work with among the Objective-C, Java and PhoneGap, by far. I created the app as easily as

Step 1. Write the app and test it in Browser using the Chrome developer tools. Step 2. Start a project in Xcode. Step 3. Copy the HTML and CSS files to project directory and export to simulator.

The experience was very good, (After spending time with Obj-C and Java), as I could use a Chrome console as a repl, something which I sorely missed.

The exported app does look native, with controls which look coming from browser. But with some CSS you can go a long way here.

Getting started

1. Get the Xcode and the Iphone SDK.
2. Download PhoneGap and install from PhoneGap iOS, this will create a new user template for PhoneGap in Xcode.
3. Create a PhoneGap project in Xcode.
4. Edit the www/index.html

Code like it is the web

I don't like working with the code->compile->check in simulator cycle. You can work much faster if you work with the browser.

I edited the index.html, adding the Jquery library for easy DOM manipulation, and a bit of CSS to align.

Lay out the Layout

You can layout your UI using the common HTML elements. Here is a snippet from the finished app.

 <div class="input">
    <label>
        Your investments under 80D are:
    </label>
    <input type="number"  placeholder=0 id="infra_investment"></input>
</div>

 <div class="input">
    <label>
        Your housing loan interests paid are:
    </label>
    <input type="number"  placeholder=0 id="housing_interest"></input>
</div>

These are standard HTML5 elements. Note that we were able to use HTML5 only elements like

type="number"  placeholder=0

which set the keyboard type and placeholder which you can do via android:inputType or editing in Interface Builder.

Code the code

We will write the code to get the input values and then calculate the tax. We are using Jquery functions for UI manipulation. Here is what the code looks like.

        $("#calculate_tax").click(function(){
        income = $("#income").val();
        investment = $("#investment").val();
        infra_investment = $("#infra_investment").val();
        housing_interest = $("#housing_interest").val();
        medical_premium =  $("#medical_premium").val();
        console.log(""+income+investment+infra_investment+housing_interest+medical_premium);
        if (!income){
            income = 0;
        }
        .....
            var tax = calculateTax(income, investment, infra_investment, housing_interest, medical_premium);
            console.log(""+tax);            
            calculated_tax  = $("#calculated_tax");
            calculated_tax.html(tax);
        });

        function getTax(taxableIncome){
        .....

Full listing here

Put on iPhone

Once you like what you see in chrome, you can put this code on simulator. Build and run from Xcode and you are done.

Resources

1. Code on github
2. Similar app using Java(For Android)
3. Similar app using Objective-C
4. Our starting Android development tutorial