用beginWithCompletionHandler替換NSOpenPanelrunModalForDirectory:的問題：

我在NSOpenPanel runModalForDirectory:用較新的beginWithCompletionHandler:.

結果并不如預期。看起來beginWithCompletionHandler:不等待用戶完成他或她的選擇！

請讓我知道我做錯了什么，或提出不同的解決方案來替換已棄用的方法。

if ([destpath isEqualToString:@""])
    {
        long result;  
        NSOpenPanel *oPanel = [NSOpenPanel openPanel];
        [oPanel setAllowsMultipleSelection:NO];
        [oPanel setCanChooseDirectories:YES];
        [oPanel setCanChooseFiles:NO];
        
        result = [oPanel runModalForDirectory:NSHomeDirectory() file:nil types:nil];
        if (result == NSModalResponseOK) 
        {
            destpath = [[oPanel URL] retain].path;
            NSLog(@"destpath is : %@", destpath);
        }
        else
            return;
    }
    
    NSLog(@"MADE IT HERE!! -- destpath is : %@", destpath);
            

我將代碼替換為：

if ([destpath isEqualToString:@""])
    {
        // long result;  // FIXED!!  Changed int to long
        NSOpenPanel *oPanel = [NSOpenPanel openPanel];
        [oPanel setAllowsMultipleSelection:NO];
        [oPanel setCanChooseDirectories:YES];
        [oPanel setCanChooseFiles:NO];
                
        [oPanel beginWithCompletionHandler:^(NSInteger result) {
            if(result == NSModalResponseOK) {
                destpath = [[oPanel URL] retain].path;
                NSLog(@"destpath is : %@", destpath);
                }
            else
                return;
        }];
        
    }
    
    NSLog(@"MADE IT HERE!! -- destpath is : %@", destpath);
        

當我運行原始代碼時，我看到以下 NSLog 訊息：

022-09-04 12:20:18.175924-0400 iRipCD[69097:3332748] destpath is : /Users/grinch/Downloads
2022-09-04 12:20:18.175982-0400 iRipCD[69097:3332748] MADE IT HERE!! -- destpath is : /Users/grinch/Downloads

但是新代碼不起作用。該程式不會等待用戶完成他或她對所需目錄的選擇。我看到以下 NSLog 訊息：

2022-09-04 12:15:30.595589-0400 iRipCD[68991:3329339] MADE IT HERE!! -- destpath is :

2022-09-04 12:15:34.320552-0400 iRipCD[68991:3329339] destpath is : /Users/grinch/Downloads

僅供參考 - destpath 在同一個檔案中更早地被初始化：

- (id)init
{
    self = [super init];

    task = nil;
    timer = nil;
    destpath = @"";
    taskOutput = [[NSMutableString alloc] init];
    fileList = [[NSMutableArray alloc] initWithCapacity:15];

    [(id) [NSApp delegate] setMaster:self];  // FIXED THIS!!  Added (id)

    return self;
}

uj5u.com熱心網友回復：

看起來必須使用一個runModal來確保 NSOpenPanel 物件等待用戶選擇目錄。

該beginWithCompletionHandler:方法不等待用戶完成他或她的選擇。

以下代碼似乎有效：

if ([destpath isEqualToString:@""])
{
    NSOpenPanel *oPanel = [NSOpenPanel openPanel];

    [oPanel setAllowsMultipleSelection:NO];
    [oPanel setCanChooseDirectories:YES];
    [oPanel setCanChooseFiles:NO];

    // 
    // N.B. -- beginWithCompletionHandler: does not wait for the
    // user to finish with his or her selection!
    //               
    //[oPanel beginWithCompletionHandler:^(NSInteger result) {
    //     if(result == NSModalResponseOK) {
    //
    // Use runModal to ensure that the program waits for the user
    // to finish with his or her selection!
    //

    if ([oPanel runModal] == NSModalResponseOK)
    {
        destpath = [[[oPanel URL] path] retain]  // Also fixed memory bug!
        NSLog(@"destpath is : %@", destpath);
    }
    else
        return;         
 }

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