如何保存在Objective-C

Question

一個應用程序我正在開發在Objective-C的iPhone應用程序的資源文件夾中的文件。我的問題是，我的應用程序必須保存從網址獲取的圖像。我認爲該文件夾是隻讀的。這是我的代碼保存圖像：

-(void)banner:(NSString *)path{ 
    NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: path]]; 
    UIImage *image = [UIImage imageWithData: imageData]; 
    NSString* resourcePath = [[NSBundle mainBundle] resourcePath]; 
    NSString* pathEnd = [resourcePath stringByAppendingFormat:@"/banner.png"]; 
    NSData *data1 = [NSData dataWithData:UIImagePNGRepresentation(image)]; 
    NSError *writeError = nil; 
    [data1 writeToFile:pathEnd options:NSDataWritingAtomic error:&writeError]; 
} 

但是當我找回圖像，它不是文件夾中。我能做什麼？

Answer 1

你不能，該應用程序包是隻讀的。您應該將任何數據保存在文檔或緩存目錄中。

-(void)banner:(NSString *)path{ 
    NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: path]]; 
    UIImage *image = [UIImage imageWithData: imageData]; 

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); 
    NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"banner.png"]; 

    NSData *data1 = [NSData dataWithData:UIImagePNGRepresentation(image)]; 
    NSError *writeError = nil; 

    [data1 writeToFile:filePath options:NSDataWritingAtomic error:&writeError]; 

    if (writeError) { 
     NSLog(@"Error writing file: %@", writeError); 
    } 
} 

是否有任何理由再對數據的第一和背面將圖像轉換成NSData對象？

如果沒有，你可能只是這樣做：

-(void)banner:(NSString *)path{ 
    NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: path]]; 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);         NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"banner.png"];  
    NSError *writeError = nil; 
    [imageData writeToFile:filePath options:NSDataWritingAtomic error:&writeError]; 

    if (writeError) { 
     NSLog(@"Error writing file: %@", writeError); 
    } 
}