how to insert number like in stack and delete like pop - ios

Question

I am using buttons and I assigned tag 0 to 10 . Then I made an action to get the clicked button's tag, and now I want to display the tag in a label . Also I have a cancel button C. If user wants to delete any number, he can click C button that I want to remove number from the label .
This is my screenshot to touch the number
- (void)viewDidLoad {
[super viewDidLoad];
self.title = #"Ezywire";
addnum=[[NSMutableArray alloc]init];
numbber=[[NSString alloc]init];
}
- (IBAction)NumberAction:(id)sender {
NSInteger tagvalue = [sender tag];
NSString *current=[NSString stringWithFormat:#"%ld", (long)tagvalue];
[addnum addObject:current];
NSString *temp;
for ( int i=0; i<[addnum count]; i++) {
numbber=[numbber stringByAppendingString:[addnum objectAtIndex:i]];
}
NSLog(#"data===%#",numbber);
ValueLable.text= numbber;
}
But in the label I am getting repeated number like this. How to implement this.
For example if user enters 2 then in the label
2
then he enters 7 then in the label
27
then he entered 9 then in the label
279
........ like this .
If user clicks C, then it remove from label last value is (last value removed)
27

Answer 1

The problem in your code is that numbber is initialized when the view is loaded, and never gets cleared again. However, each time a button is pressed, the whole addnum of digits gets appended to num again, creating repeated digits.
Fix this by removing num as an instance variable, making it a local to NumberAction: method, and setting it to an empty string every time the number is pressed.
Since you are planning to support the clearing action as well, you should make a private method that combines the digits from addnum array into a string. This way your NumberAction: and ClearAction would share the code that formats the array and sets the label. Your NumberAction: method would append a number and call FormatAndSetLabel, while the ClearAction method would remove the last digit if it is available, and call FormatAndSetLabel as well:
- (IBAction)NumberAction:(id)sender {
NSInteger tagvalue = [sender tag];
NSString *current=[NSString stringWithFormat:#"%ld", (long)tagvalue];
[addnum addObject:current];
[self FormatAndSetLabel];
}
- (IBAction)ClearAction:(id)sender {
if (!addnum.count) return;
[addnum removeLastObject];
[self FormatAndSetLabel];
}
-(void)FormatAndSetLabel {
NSMutableString *temp = [NSMutableString string];
for ( int i=0; i<[addnum count]; i++) {
[temp appendString:addnum[i]];
}
ValueLable.text= temp;
}

Answer 2

Also it might be interesting for you to have a look at Paul's Hegarty Stanford iOS development course (iPad and iPhone Application Development, Fall 2011)
https://itunes.apple.com/ru/itunes-u/ipad-iphone-application-development/id473757255?mt=10
Calculator app is used here as an example. Must see for the beginners.