Concatenate a NSInteger to NSInteger - ios

Question

i'm making my own calculator and i came to the question.
Sorry for newbie question , but I didn't find it.
How can i append a NSInteger to another NSInteger in Objective-C;
for example:
5 + 5 = 55
6 + 4 + 3 = 643
etc.

Answer 1

You have to convert them to strings. Here's one way:
NSNumber *i1 = #6;
NSNumber *i2 = #4;
NSNumber *i3 = #3;
NSMutableString *str = [NSMutableString new];
[str appendString:[i1 stringValue]];
[str appendString:[i2 stringValue]];
[str appendString:[i3 stringValue]];
NSLog(#"result='%#", str);
However, having said all that, it's not clear to me why you are concatenating at all.

Answer 2

If they are a single digit (as in a calculator) you can simply do:
NSInteger newNumber = (oldNumber * 10) + newDigit;
or in a method:
- (NSInteger)number:(NSInteger)currentNumber byAdding:(NSInteger)newDigit {
//Assumes 0 <= newDigit <= 9
return (currentNumber * 10) + newDigit;
}
If they have more than one digit you can make them into strings, concatenate them and convert back to integers or use simple arithmetic to find out the power of 10 you must multiply by.
EDIT: 6 + 4 + 3 Assuming a digit is provided at a time:
NSInteger result = [self number:[self number:6 byAdding:4] byAdding:3];
Purely arithmetic solution:
- (NSInteger)powerOfTenForNumber:(NSInteger)number {
NSInteger result = 1;
while (number > 0) {
result *= 10;
number /= 10;
}
return result;
}
- (NSInteger)number:(NSInteger)currentNumber byAdding:(NSInteger) newNumber {
return (currentNumber * [self powerOfTenForNumber:newNumber]) + newNumber;
}