[OC Foundation框架 - 2] NSString 的创建

A. 不可变字符串

 void stringCreate()
 {
     //Don't need to release memory by this way
     NSString *str1 = @"String Sample";

     NSString *str2 = [[NSString alloc] init];
     str2 = @"String sample 2";
     [str2 release];

     NSString *str3 = [[NSString alloc] initWithString:@"String sample 3"];
     [str3 release];
     //Don't need to manage memory by static function
     str3 = [NSString stringWithString:@"A String"];

     NSString *str4 = [[NSString alloc] initWithUTF8String:"String sample4"];
     [str4 release];
     //No manual memory management, too
     str4 = [NSString stringWithUTF8String:"String 4"];

     NSString *str5 = [[NSString alloc] initWithFormat:@"My age is %i and height is %.2f", , 1.55];
     NSLog(@"String 5 is %@", str5);
     [str5 release];
 }

 

B. 从文件读取字符串

 void readFromFile()
 {
     NSString *path = @"/Users/hellovoidworld/Study/Foundation/NSString/file.txt";

     //This function cannot read Chinese, is expired
 //    NSString *str1 = [NSString stringWithContentsOfFile:path];

     NSError *error;

     NSString *str1 = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];

     if (error == nil)
     {
         NSLog(@"Read successfully, is %@", str1);
     }
     else
     {
         NSLog(@"Read fail, error is %@", error);
     }
 }

 

C. 从URL读取

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