Understanding Objective-C and Adding a “$” to a Tip Calculator

Overview

In this article, we will explore the process of adding a “$” symbol to a tip calculator written in Objective-C. The code is provided as a copy-paste snippet, but for clarity, it will be reorganized into sections.

Introduction to Objective-C and iOS Development

Objective-C is a high-level programming language developed by Apple Inc. It is primarily used for developing iOS applications. In this article, we will focus on adding a “$” symbol to a tip calculator using Objective-C.

Understanding the Code

The provided code snippet appears to be part of a tipcalcViewController class. This class has several methods and variables that are related to calculating tips based on user input. The main methods of interest in this context are:

• - (IBAction)aSliderChanged:(id)sender
• - (void)viewDidLoad
• - (void)textFieldDidEndEditing:(UITextField *)textField

These methods handle the user interface events, such as when a slider’s value changes or when editing text fields.

Identifying the Issue

The main issue with this code is that it doesn’t properly format the currency. The tip amount and cost without tip are being displayed as floats but not formatted correctly to display “$” symbol.

Solution: Formatting Currency using NSNumberFormatter

In Objective-C, you can use NSNumberFormatter to format numbers as currencies. This class provides a convenient way to convert between NSNumber objects and string representations of numbers in various formats, including currency.

To fix the issue, we need to replace the hardcoded formatting with code that uses NSNumberFormatter. We’ll do this by importing the NSNumberFormatter class and creating an instance of it to format our number as currency.

Code Changes

Here’s an updated version of the relevant parts of the code:

- (IBAction)aSliderChanged:(id)sender {
    // ...
    if (slider == tipslide) {
        NSNumber *tip = [NSNumber numberWithFloat:slider.value * 100];
        NSNumberFormatter *currencyFormatter = [[NSNumberFormatter alloc] init];
        [currencyFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
        NSString *formattedTip = [currencyFormatter stringFromNumber:tip];
        // ...
    }
    // ...
}

- (void)viewDidLoad {
    // ...
    [costWithoutTip becomeFirstResponder];
    [costWithoutTip setDelegate:self];
    [costWithoutTip setKeyboardType:UIKeyboardTypeNumbersAndPunctuation];
    // Create a number formatter for currency
    NSNumberFormatter *currencyFormatter = [[NSNumberFormatter alloc] init];
    [currencyFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
    costWithoutTipFormatter = currencyFormatter;
    // ...
}

In the updated code, we create an instance of NSNumberFormatter and set its style to NSNumberFormatterCurrencyStyle. We then use this formatter to convert our numbers into strings that include the “$” symbol.

Additional Advice

When working with numbers in iOS development, using NSNumberFormatter is often the best way to format them as currency. This class provides a lot of flexibility and can be used to customize how your numbers are displayed.

Last modified on 2024-02-16