[OC Foundation框架

A. 不可变字符串

 1 void stringCreate()
 2 {
 3     //Don't need to release memory by this way
 4     NSString *str1 = @"String Sample";
 5    
 6     NSString *str2 = [[NSString alloc] init];
 7     str2 = @"String sample 2";
 8     [str2 release];
 9    
10     NSString *str3 = [[NSString alloc] initWithString:@"String sample 3"];
11     [str3 release];
12     //Don't need to manage memory by static function
13     str3 = [NSString stringWithString:@"A String"];
14    
15     NSString *str4 = [[NSString alloc] initWithUTF8String:"String sample4"];
16     [str4 release];
17     //No manual memory management, too
18     str4 = [NSString stringWithUTF8String:"String 4"];
19    
20    
21     NSString *str5 = [[NSString alloc] initWithFormat:@"My age is %i and height is %.2f", 19, 1.55];
22     NSLog(@"String 5 is %@", str5);
23     [str5 release];
24 }

B. 从文件读取字符串

 1 void readFromFile()
 2 {
 3     NSString *path = @"/Users/hellovoidworld/Study/Foundation/NSString/file.txt";
 4    
 5     //This function cannot read Chinese, is expired
 6 //    NSString *str1 = [NSString stringWithContentsOfFile:path];
 7    
 8     NSError *error;
 9    
10     NSString *str1 = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];
11    
12     if (error == nil)
13     {
14         NSLog(@"Read successfully, is %@", str1);
15     }
16     else
17     {
18         NSLog(@"Read fail, error is %@", error);
19     }
20 }

C. 从URL读取

1 void readFromUrl()
2 {
3     NSURL *url = [NSURL URLWithString:@"file:///Users/hellovoidworld/Study/Foundation/NSString/file.txt"];
4     NSString *str2 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
5     NSLog(@"Read url successfully, is %@", str2);
6 }