NSString *string = @"";

// 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 = ;

// 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];