NSString *tempA = @"123";

NSString *tempB = @"456";

// 1，字符串拼接

NSString *newString = [NSString stringWithFormat:@"%@%@",tempA,tempB];

//2，字符转NSInteger      NSInteger k = [newString integerValue];

//2，NSInteger转字符      NSString *s = [NSString stringWithFormat:@"%ld",k];

//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];