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문자를 숫자로 ( String -> int, float, double, ... )

NSString *aString = @"111";

int aInt = [aString intValue];

float aFloat = [aString floatValue];

double aDouble = [aString doubleValue];

NSLog(@"aInt = %d", aInt);

NSLog(@"aFloat = %f", aFloat);

NSLog(@"aDouble = %d", aDouble);

숫자를 문자로 ( int, float, double, ... -> String )

아래와 같이 stringWithFormat을 이용한다.

NSString* aIntStr = [NSString stringWithFormat:@"%d", aInt];

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NSString to float, float to NSString

NSString *string = @"0.5";

float result = 0.3 + [string floatValue];

NSLog(@"result = %f", result);

NSLog(@"trimmedResult = %.1f", result);

NSString *floatResultToString = [NSString stringWithFormat:@"%f", result];

NSLog(@"floatResultToString = %@", floatResultToString);

NSString to Int, int to NSString

NSString *string2 = @"2";

int result2 = 3 + [string2 intValue];

NSLog(@"result2 = %d", result2);

NSString *intResultToString = [NSString stringWithFormat:@"%d", result2];

NSLog(@"intResultToString = %@", intResultToString); //Be sure to not using %d, it will cause unexpected error.

NSData to NSString, NSString to NSData

NSString *string3 = @"한글(any unicode character include Korean, Japanese, Chinese)";

NSData *aData = [string3 dataUsingEncoding:NSUTF8StringEncoding];

NSString *string4 = [[NSString alloc] initWithData:aData encoding:NSUTF8StringEncoding];

NSLog(@"string4 = %@", string4);

NSDate to NSString 

NSDate *today = [NSDate date];

//NSLog(@"todayDateString = %@", [today descriptionWithLocale:[NSLocale currentLocale]]);

NSLog(@"todayDateString = %@", [today description]); // it will return YYYY-MM-DD HH:MM:SS GMT

BOOL to NSString, NSString to BOOL

NSString *boolYesString = @"YES";

BOOL aBOOL = [boolYesString boolValue];

if (aBOOL) {

NSLog(@"aBOOL is YES");

}

Int to NSNumber

NSNumber *myNumber = [NSNumber numberWithInt:3];

NSLog(@"myNumber=%@", myNumber);

Double to NSString, NSString to Double

NSString *theString = @"123";

double theDouble = [theString doubleValue];

NSLog(@"theDouble = %f", theDouble);

NSString *doubleString = [NSString stringWithFormat:@"%f", theDouble];

NSLog(@"doubleString = %@", doubleString);

NSString *doubleString2Digit = [NSString stringWithFormat:@"%.2f", theDouble];

NSLog(@"doubleString with 2digit Decimal Point = %@", doubleString2Digit);

NSData to UIImage

NSData *imageData = UIImagePNGRepresentation(image);

UIImage *image=[UIImage imageWithData:data];

출처: https://comxp.tistory.com/238 [까칠하게...]