Objective-C NSString/字符串 - Objective-C教程

在Objective-C编程语言的字符串表示使用NSString 和它的子类NSMutableString的创建字符串对象提供了几种方法。创建一个字符串对象最简单的方法是使用 Objective-C 的@"..."构造：

NSString *greeting = @"Hello";

一个简单的例子，用于创建和打印字符串如下所示。

#import <Foundation/Foundation.h>

int main ()
{
   NSString *greeting = @"Hello";
   NSLog(@"Greeting message: %@
", greeting );
   return 0;
}

上面的代码编译和执行时，它产生的结果如下：

2013-09-11 01:21:39.922 demo[23926] Greeting message: Hello

Objective-C的支持范围广泛的操作字符串的方法：

S.N.	方法 & 目的
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-yiibai value of the receiver’s text as a double.
4	- (float)floatValue; Returns the floating-yiibai 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.

下面的示例，如何使用几个上述功能：

#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 :  %@
", str3 );

   /* concatenates str1 and str2 */
   str3 = [str1 stringByAppendingFormat:@"World"];
   NSLog(@"Concatenated string:   %@
", str3 );

   /* total length of str3 after concatenation */
   len = [str3 length];
   NSLog(@"Length of Str3 :  %d
", len );

   /* InitWithFormat */
    str3 = [[NSString alloc] initWithFormat:@"%@ %@",str1,str2];    
    NSLog(@"Using initWithFormat:   %@
", str3 );
    [pool drain];

   return 0;
}

上面的代码编译和执行时，它产生的结果如下：

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

可以找到一个完整的列表Objective-C中的NSString相关方法 NSString 类参数.