i am retrieving different characters from a string by using thsi function and adding 5 to them to display the corresponding character for eg. 'a' displays 'f' and 'h' displays 'm'.. but the problem is that i am not able to add these characters into a string which i can use to display to display like 'fm'...can anyone help?? heres the code strResult(mutablestring) is getting null only.

`str=@"John";

int a=[str length];

for(i=0;i

char ch=[str characterAtIndex:i];

ch=ch+5;

temp=[NSString stringWithFormat:@"%c",ch];

[strResult appendString:temp];

NSLog(@"%c",ch);

}`