Objective-C Strings
The string in Objective-C programming language is represented using NSString and its subclass NSMutableString provides several ways for creating string objects. The simplest way to create a string object is to use the Objective-C @”…” construct −
NSString *greeting = @"Hello";
A simple example for creating and printing a string is shown below.
#import <Foundation/Foundation.h> int main () { NSString *greeting = @"Hello"; NSLog(@"Greeting message: %@n", greeting ); return 0; }
When the above code is compiled and executed, it produces result something as follows −
2013-09-11 01:21:39.922 demo[23926] Greeting message: Hello
Objective-C supports a wide range of methods for manipulate strings −
Sr.No. | Method & Purpose |
---|---|
1 |
– (NSString *)capitalizedString; Returns a capitalized representation of the receiver. |
2 |
– (unichar)characterAtIndex:(NSUInteger)index; Returns the character at a given array position. |
3 |
– (double)doubleValue; Returns the floating-point value of the receiver’s text as a double. |
4 |
– (float)floatValue; Returns the floating-point value of the receiver’s text as a float. |
5 |
– (BOOL)hasPrefix:(NSString *)aString; Returns a Boolean value that indicates whether a given string matches the beginning characters of the receiver. |
6 |
– (BOOL)hasSuffix:(NSString *)aString; Returns a Boolean value that indicates whether a given string matches the ending characters of the receiver. |
7 |
– (id)initWithFormat:(NSString *)format …; Returns an NSString object initialized by using a given format string as a template into which the remaining argument values are substituted. |
8 |
– (NSInteger)integerValue; Returns the NSInteger value of the receiver’s text. |
9 |
– (BOOL)isEqualToString:(NSString *)aString; Returns a Boolean value that indicates whether a given string is equal to the receiver using a literal Unicode-based comparison. |
10 |
– (NSUInteger)length; Returns the number of Unicode characters in the receiver. |
11 |
– (NSString *)lowercaseString; Returns lowercased representation of the receiver. |
12 |
– (NSRange)rangeOfString:(NSString *)aString; Finds and returns the range of the first occurrence of a given string within the receiver. |
13 |
– (NSString *)stringByAppendingFormat:(NSString *)format …; Returns a string made by appending to the receiver a string constructed from a given format string and the following arguments. |
14 |
– (NSString *)stringByTrimmingCharactersInSet:(NSCharacterSet *)set; Returns a new string made by removing from both ends of the receiver characters contained in a given character set. |
15 |
– (NSString *)substringFromIndex:(NSUInteger)anIndex; Returns a new string containing the characters of the receiver from the one at a given index to the end. |
Following example makes use of few of the above-mentioned functions −
#import <Foundation/Foundation.h> int main () { NSString *str1 = @"Hello"; NSString *str2 = @"World"; NSString *str3; int len ; NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; /* uppercase string */ str3 = [str2 uppercaseString]; NSLog(@"Uppercase String : %@n", str3 ); /* concatenates str1 and str2 */ str3 = [str1 stringByAppendingFormat:@"World"]; NSLog(@"Concatenated string: %@n", str3 ); /* total length of str3 after concatenation */ len = [str3 length]; NSLog(@"Length of Str3 : %dn", len ); /* InitWithFormat */ str3 = [[NSString alloc] initWithFormat:@"%@ %@",str1,str2]; NSLog(@"Using initWithFormat: %@n", str3 ); [pool drain]; return 0; }
When the above code is compiled and executed, it produces result something as follows −
2013-09-11 01:15:45.069 demo[30378] Uppercase String : WORLD 2013-09-11 01:15:45.070 demo[30378] Concatenated string: HelloWorld 2013-09-11 01:15:45.070 demo[30378] Length of Str3 : 10 2013-09-11 01:15:45.070 demo[30378] Using initWithFormat: Hello World
You can find a complete list of Objective-C NSString related methods in