Sending 'void' to parameter of incompatible type 'id'

Question

In Objective C, I have:

NSMutableArray *retVal = [[NSMutableArray alloc]initWithCapacity:1];
NSMutableString *justTest = [[NSMutableString alloc]initWithString:@"hello"];
unsigned char ch = //anything
[retVal insertObject:[justTest appendFormat:@"%hhu", ch] atIndex:0]; //error here

X Code 5.1.1 gives me an error in the 4th line(as mentioned as comment) as Sending 'void' to parameter of incompatible type 'id'

What am I doing wrong here? Any help is appreciated.

Answer 1

appendFormat doesn't return anything, it adjusts the mutable string. You need to do this:

NSMutableArray *retVal = [[NSMutableArray alloc]initWithCapacity:1];
NSMutableString *justTest = [[NSMutableString alloc]initWithString:@"hello"];
unsigned char ch = //anything
[justTest appendFormat:@"%hhu", ch]
[retVal insertObject:justTest atIndex:0]; //error here