NSString *string = @"123";

// 1.字符串转int
int intString = [string intValue];

// 2.int转字符串
NSString *stringInt = [NSString stringWithFormat:@"%d",intString];

// 3.字符串转float
float floatString = [string floatValue];

// 4.float转字符串
NSString *stringFloat = [NSString stringWithFormat:@"%f",floatString];


  long longValue = 104024;    
// 5.long 型转换字符串
 NSNumber *longNumber = [NSNumber numberWithLong:longValue];
NSString *longStr = [longNumber stringValue];
        
 // 6.long long 型转换字符串
NSNumber *longlongNumber = [NSNumber numberWithLongLong:longValue];
NSString *longlongStr = [longlongNumber stringValue];

//7.字符串转long
[str longLongValue];