NSString *tempA = @"123";
NSString *tempB = @"456";
1，字符串拼接
 NSString *newString = [NSString stringWithFormat:@"%@%@",tempA,tempB];
2，字符转int
int intString = [newString intValue];
3，int转字符
NSString *stringInt = [NSString stringWithFormat:@"%d",intString];
4，字符转float
 float floatString = [newString floatValue];
5，float转字符
NSString *stringFloat = [NSString stringWithFormat:@"%f",intString];