NSOutlineView的IBOutlet未指向有效实例

Question

我在Xcode中创建了一个新的Cocoa应用程序项目，然后在窗口上添加了NSOutlineView和NSTextView对象。这两个对象被子类化为MyOutlineView和MyTextView。之后，我为他们创建了两个出口，并编写了如下代码。

我发现，问题是应用程序在运行时有两个不同的MyOutlineView实例。工作（有效）大纲视图实例不等于myOutlineView插座实例。我错过了什么？

//
//  AppDelegate.h

#import <Cocoa/Cocoa.h>
#import "MyOutlineView.h"
#import "MyTextView.h"

@interface AppDelegate : NSObject <NSApplicationDelegate>

@property (assign) IBOutlet NSWindow *window;
@property (weak) IBOutlet MyOutlineView *myOutlineView;
@property (unsafe_unretained) IBOutlet MyTextView *myTextView;

@end

//
//  AppDelegate.m

#import "AppDelegate.h"

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)n
{
    NSLog(@"AppDelegate.myOutlineView(INVALID)::%@", _myOutlineView);
    NSLog(@"AppDelegate.myTextView::%@", _myTextView);
}

@end

//
//  MyOutlineView.h

#import <Cocoa/Cocoa.h>

@interface MyOutlineView : NSOutlineView <NSOutlineViewDataSource>;

@end

//
//  MyOutlineView.m

#import "MyOutlineView.h"

@implementation MyOutlineView

- (id)initWithCoder:(NSCoder *)aDecoder
{
    // This method is called first.
    self = [super initWithCoder:aDecoder];
    NSLog(@"MyOutlineView initWithCoder(INVALID)::%@", self);
    return self;
}

- (id)initWithFrame:(NSRect)frame
{
    // This method is also called but through a different instance with first one.
    self = [super initWithFrame:frame];
    NSLog(@"MyOutlineView initWithFrame(valid)::%@", self);
    return self;
}

- (NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item
{
    NSLog(@"MyOutlineView data source delegate(valid)::%@", self);
    return 0;
}

- (id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)index ofItem:(id)item
{
    return nil;
}

- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item
{
    return NO;
}

@end

//
//  MyTextView.h

#import <Cocoa/Cocoa.h>

@interface MyTextView : NSTextView

@end

//
//  MyTextView.m

#import "MyTextView.h"

@implementation MyTextView

- (id)initWithCoder:(NSCoder *)aDecoder
{
    // This method is called.
    self = [super initWithCoder:aDecoder];
    NSLog(@"MyTextView initWithCoder::%@", self);
    return self;
}

- (id)initWithFrame:(NSRect)frame
{
    // But this method is NOT called at all.
    self = [super initWithFrame:frame];
    NSLog(@"MyTextView initWithFrame::%@", self);
    return self;
}

@end

输出：

MyTextView initWithCoder::                 [MyTextView: 0x10013be80]
MyOutlineView initWithCoder(INVALID)::     [MyOutlineView: 0x10014bc90]
MyOutlineView initWithFrame(valid)::       [MyOutlineView: 0x1001604a0]
MyOutlineView data source delegate(valid)::[MyOutlineView: 0x1001604a0]
AppDelegate.myOutlineView(INVALID)::       [MyOutlineView: 0x10014bc90]
AppDelegate.myTextView::                   [MyTextView: 0x10013be80]

因此，我必须把“AppDelegate.myOutlineView = self;”进入MyOutletView的实现，只要它调用AppDelegate的相关方法。这似乎并不自然。

Answer 1

Xcode似乎不允许您将大纲视图的委托或数据源设置为自身。

所以我猜你正在做这样的事情：

也就是说：实例化自定义大纲视图类的第二个副本。

以下是此设置的输出：

2012-09-26 14:11:34.511 testproj[30255:403] -[MyOutlineView initWithCoder:]
2012-09-26 14:11:34.531 testproj[30255:403] -[MyOutlineView initWithFrame:]

通过删除“我的大纲视图”的额外（突出显示）实例，initWithFrame:行消失。

要使大纲视图成为自己的委托，请改为：

- (void) awakeFromNib {
    self.delegate = self;
}

尽管如此，委托模式的重点是避免了子类化的需要。如果做需要大纲视图子类，请尝试直接覆盖NSOutlineView / NSTableView方法，而不是使用委托协议。

Answer 2

我无法重现你的问题。我将您发布的所有代码都放到了测试应用程序中，我只获得了每个对象的一个​​实例。我尝试时都没有调用initWithFrame方法。我的输出是：

2012-09-26 09:00:38.945 TextViewDoubleInstantiationProblem[451:303] MyTextView initWithCoder::<MyTextView: 0x100123990>
    Frame = {{0.00, 0.00}, {381.00, 182.00}}, Bounds = {{0.00, 0.00}, {381.00, 182.00}}
    Horizontally resizable: NO, Vertically resizable: YES
    MinSize = {381.00, 182.00}, MaxSize = {463.00, 10000000.00}
2012-09-26 09:00:38.953 TextViewDoubleInstantiationProblem[451:303] MyOutlineView initWithCoder(INVALID)::<MyOutlineView: 0x101a1cb90>
2012-09-26 09:00:39.005 TextViewDoubleInstantiationProblem[451:303] AppDelegate.myOutlineView(INVALID)::<MyOutlineView: 0x101a1cb90>
2012-09-26 09:00:39.005 TextViewDoubleInstantiationProblem[451:303] AppDelegate.myTextView::<MyTextView: 0x100123990>
    Frame = {{0.00, 0.00}, {381.00, 182.00}}, Bounds = {{0.00, 0.00}, {381.00, 182.00}}
    Horizontally resizable: NO, Vertically resizable: YES
    MinSize = {381.00, 182.00}, MaxSize = {463.00, 10000000.00}

您的应用中是否还有其他未显示的代码？

Answer 3

对initWithCoder:的调用来自加载nib文件中定义的对象。我认为，自从你提到创建网点以来，这就是你想要发生的事情。在这种情况下，他们打电话给initWithFrame:让我觉得比编码员更有可能“无效”。

我在initWithFrame:设置了一个断点，并跟踪该来电的来源，以确定额外的分配。