Model-View-Controller Since a calculator is something that might be used in various situations, you decide to rewrite your code to something more reusable. One advantage of MVC is that you can exchange the view but keep your model and parts of your controller. We provide you with a template for a class called BasicCalculator. Extend that class to provide a fully functional basic calculator. This class is your model.

The provided template is similar to the one from Assignment #1, where the calculator functionality is moved to the new model class. You could either use your code from the previous assignment and adjust it or redo the changes from the previous assignment inside the new template. Here we will choose the second approach.

First link the missing number buttons to the view controller class and change the tags of the buttons accordingly.
Continue reading “iOS Dev – Assignment #2 – Task #1”

Visualize the currently active operation by letting the button be pushed until the second operand is entered.

A button can be displayed as pushed by “highlighting”. However, when the resultButtonPressed: method fires, the button is already highlighted and will be dehighlighted shortly after. Thus it is necessary to “wait a little bit” actually till the “normal button functionality” has finished before highlighting the button. This can be achieved by adding an operation on the main queue.
To remove the highlighting, add a property to hold the currently pressed button.

@property (nonatomic, strong) UIButton *currentButton;

- (IBAction)operationButtonPressed:(UIButton *)sender {
	...
	else
	{
		...
		self.currentButton.highlighted = NO;
	}
	...
	[[NSOperationQueue mainQueue] addOperationWithBlock:^{
		sender.highlighted = YES;
		self.currentButton = sender;
	}];
}

- (IBAction)resultButtonPressed:(id)sender {
	...
	self.currentButton.highlighted = NO;
}

- (IBAction)clearDisplay:(id)sender {
	...
	self.currentButton.highlighted = NO;
}

Adapt the number of shown decimals to the actual result that is to be displayed.

Actually NSNumber does that all. Thus we just have to create an NSNumber from the number before we display it. At the same time we change all floats to doubles to reduce the problem of the “float feature” described before:

- (IBAction)operationButtonPressed:(UIButton *)sender {
    ...
    self.numberTextField.text = [NSString stringWithFormat:@"%@", 
         [NSNumber numberWithDouble:firstOperand]];        
    ...
}

- (IBAction)resultButtonPressed:(id)sender {
    ...
    self.numberTextField.text = [NSString stringWithFormat:@"%@", [NSNumber numberWithDouble:result]];
    ...
}

We provide you with a template for a calculator that already adds numbers (at least 1 and 2).
Take a close look at the implementation of this template and write the necessary code to have a fully working calculator.

Let’s have a look at the number buttons:

Continue reading “iOS Dev – Assignment #1”