Question

For a school assignment I have been told to make a calculator app, the same as the spotlight calculator. It works in realtime and has no buttons for things to begin.

So far this is my code. It is written in a text field with the event Editing Did End. Im pretty sure thats wrong but i can’t find an alternative solution. Also i haven’t gotten the realtime thing to work so i’ve kind of reverted to completing the following steps when pressed off the text field.

- (IBAction)Didend_Action:(id)sender {
  NSString *list = [Sum_TextField text]; 
  NSArray *listItemsArray = [list componentsSeparatedByString:@" "];
  float firstNumber = [[listItemsArray objectAtIndex: 0] floatValue]; 
  NSString *symbol = [listItemsArray objectAtIndex: 1];
  float secondNumber = [[listItemsArray objectAtIndex: 2] floatValue];
  {   
    Calculator* calc = [[Calculator alloc] init];
    [calc setNum1:firstNumber];
    [calc setNum2:secondNumber];
    if ([symbol isEqualToString:@"-"])
    {
        [calc minus];
    }
    else if ([symbol isEqualToString:@"+"])
    {
        [calc add];
    } 
    if ([symbol isEqualToString:@"*"])
    {
        [calc multiply];
    }
    else if ([symbol isEqualToString:@"/"])
    {
        [calc divide];

    }
    [Answer_TextField setText:[NSString stringWithFormat:@"%d", [calc answer]]];  
  }
}

Answer 1

I think a better way to do it would be to implement the UITextViewDelegate protocol methods like textViewDidChange:. For example, you could do something like this:

- (void)textViewDidChange:(UITextView *)textView {

    NSString *currentText = [textview text];
    NSArray *currentItems = [currentText componenetsSeparatedByString:@" "];
    float result = 0.0;

    //If a valid expression is in the text view
    if([currentItems count] > 2) {

        float num1 = [[currentItems objectAtIndex:0] floatValue];
        float num2 = [[currentItems objectAtIndex:2] floatValue];
        NSString *operator = [currentItems objectAtIndex:1];

        if([operator isEqualToString:@"+"]) {

            result = num1 + num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];
        }
        else if([operator isEqualToString:@"-"]) {

            result = num1 - num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];
        }
        else if([operator isEqualToString:@"*"]) {

            result = num1 * num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];
        }
        else if([operator isEqualToString:@"/"]) {

            result = num1 / num2;
            answerTextField.text = [NSString stringWithFormat:@"%f", result];            
        }
        else{

            answerTextField.text = @"Invalid Operation";
        }
    }
} 

This would be called every time the user edited the text in the text view. It should work, but I didn’t test it out. Make sure that in the header of whatever file this code is in, you do this:

@interface yourClassName : yourSuperclass <UITextViewDelegate> {

    //Your instance variables
}

//Your method and property declarations

EDIT:

Let’s say I put the - (void)textViewDidChange:(UITextView *)textView code in a file called MyClass.m. The file MyClass.m would then look like this:

@implementation MyClass

- (void)textViewDidChange:(UITextView *)textView {

    //All the above code goes here
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    //INCLUDE THESE LINES
    Sum_TextField.delegate = self;
    Answer_TextField.delegate = self;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return YES;
}

@end

In the header file (MyClass.h), I would put this:

@interface MyClass : UIViewController <UITextViewDelegate> 

//Note: you don't declare - (void)textViewDidChange:(UITextView *)textView in the header file because you are implementing
//a protocol method.

//MAKE SURE SUM_TEXTFIELD AND ANSWER_TEXTFIELD ARE UITEXTVIEWS NOT UITEXTFIELDS
@property (strong, nonatomic) IBOutlet UITextView *Sum_TextField;
@property (strong, nonatomic) IBOutlet UITextView *Answer_TextField;

@end

Hope this helps!