如何从文本文件中的特定位置使用iphone读取文本？

Question

我是新来的iphone请帮助我，我想从文本文件使用iphone中读取文本现在我能够从txtfile中读取文本，但我的问题是（在txtfile中保存了一些数据，例如“welcome to webapps”想要只读webapp字符串） 通过使用此代码，我从txtfile.please中读取所有数据，给出任何想法只读取指定的文本。

-(NSString *)readFile:(NSString *)fileName { 
    NSString *filePath = [[NSBundle mainBundle] pathForResource:fileName ofType:@"txt"]; 
    NSData *myData = [NSData dataWithContentsOfFile:filePath]; 
    NSString *str,*docStr; 

    if (myData) { 
     str = [[NSString alloc] initWithData:myData encoding:NSASCIIStringEncoding]; 

     } 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 

    // the path to write file 
    NSString *appFile = [documentsDirectory stringByAppendingPathComponent:fileName]; 
    NSError *error = nil; 
    BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:appFile]; 
    if(fileExists) 
    { 
     NSLog(@"file exist in document"); 
     NSData *myData1 = [NSData dataWithContentsOfFile:appFile]; 
     if (myData1) { 
      docStr = [[NSString alloc] initWithData:myData1 encoding:NSASCIIStringEncoding]; 

     } 
    } 
    else { 
     NSLog(@"file does not exist"); 

     BOOL success = [str writeToFile:appFile atomically:YES encoding:NSUTF8StringEncoding error:&error]; 
     if (!success) { 
      NSLog(@"Error: %@", [error userInfo]); 
     } 
     else { 
      NSLog(@"File write is successful"); 

     } 
     NSData *myData1 = [NSData dataWithContentsOfFile:appFile]; 
     if (myData1) { 
      docStr = [[NSString alloc] initWithData:myData1 encoding:NSASCIIStringEncoding]; 

     } 
    } 


    return docStr; 
} 

Answer 1

NSString *mystring=[docstr substringFromIndex:11]; 

在MyString中，你将有“的webapps”