@property retain OR copy [英] @property retain OR copy

问题描述

首先，我阅读了这篇文章

我想我应该在我的程序中使用复制。

*由于未捕获的异常NSInternalInconsistencyException而终止应用程序，原因是：' - [__ NSCFDictionary removeAllObjects]：发送到不可变对象的mutating方法

我不知道mutating method sent to immutable object。
我没有将NSDictionary设置为NSMutabledictionary指针。

这是我的代码

<

.h文件

  @interface Button：NSObject {
 
 @private 
 NSString * gID; 
 NSString * gBackColor; 
 NSString * gIconImage; 
 int gIndex; 
 BOOL gEnable; 
 BOOL gVisible; 
 NSString * gText; 
 
 NSMutableDictionary * gEvents; 
 
 
 BOOL gUseCircle; 
} 
 
 @property（nonatomic，copy）NSString * ID; 
 @property（nonatomic，copy）NSString * BackColor; 
 @property（nonatomic，copy）NSString * IconImage; 
 @property int Index; 
 @property BOOL启用; 
 @property BOOL可见; 
 @property（nonatomic，copy）NSString * Text; 
 @property（nonatomic，getter = getEvents，retain）NSMutableDictionary * Events; 
 @property BOOL UseCircle; 
 
 @end 
  

>

.m文件

  @implementation按钮
 @synthesize ID = gID; 
 @synthesize BackColor = gBackColor; 
 @synthesize IconImage = gIconImage; 
 @synthesize Index = gIndex; 
 @synthesize Enable = gEnable; 
 @synthesize Visible = gVisible; 
 @synthesize Text = gText; 
 @synthesize Events = gEvents; 
 @synthesize UseCircle = gUseCircle; 
 
  - （NSMutableDictionary *）getEvents 
 {
 if（！gEvents）
 {
 gEvents = [[NSMutableDictionary alloc] initWithCapacity：20]; 
} 
 return gEvents; 
} 
 
  - （id）init 
 {
 self = [super init]; 
 if（self！= nil）
 {
 gID = @; 
 gBackColor = @; 
 gIconImage = @; 
 gIndex = 0; 
 gText = @; 
 
 gUseCircle = NO; 
} 
 return self; 
} 
 
  - （void）dealloc 
 {
 [gID release]; 
 [gBackColor release]; 
 [gIconImage release]; 
 [gText release]; 
 
 [gEvents removeAllObjects]; 
 [gEvents release]; 
 gEvents = nil; 
 
 [super dealloc]; 
} 
  

并实现

  tBtnXML.Events = [self SplitEvents：tNode]; 
  

<

SplitEvents函数：

   - （NSMutableDictionary *）SplitEvents：（NSDictionary *）pEvents 
 { 
 NSMutableDictionary * tEvents = [[NSMutableDictionary alloc] initWithCapacity：5]; 
 //代码blabla 
 //。 
 //。 
 //。 
 [tEvents setObject：tEvent forKey：[NSNumber numberWithInt：tEventName]]; 
 [tEvent release]; 
 
 
 
 return [tEvents autorelease]; 
} 
  

但是我chage NSMutableDictionary * gEvents属性从复制到保留，它执行正常。

Colud任何人都告诉我我的代码有什么问题？

如果我的代码不正确的dealloc，请告诉我。

谢谢appriciate。
_c

是的，所以我修复了我的setter：

   - （void）setEvents ：（NSMutableDictionary *）pEvents 
 {
 NSMutableDictionary * tNewDict = [pEvents mutableCopy]; 
 [gEvents removeAllObjects]; 
 [gEvents release]; 
 gEvents = tNewDict; 
} 
  

这个工作没有错误。

它帮助了我很多。

vote up><〜

谢谢Bavarious :)

retain 而不是 copy 。当你声明一个属性为 copy 时，合成的setter方法发送 -copy 在可变对象（例如 NSMutableDictionary ）的情况下，发送 -copy 给它们使一个不可变的副本，实际上创建了一个不可变类型的对象（例如 NSDictionary ）。

因此：

  tBtnXML.Events = [self SplitEvents：tNode]; 
  / pre> 
 
 
合成设置程序将 -copy 发送到 [self SplitEvents：tNode] / code>，从而创建该字典的不可变拷贝（即 NSDictionary 实例），并将其分配给 gEvents 。这是你的错误的原因： gEvents 被声明为 NSMutableDictionary 但指向 NSDictionary 
 
 
 
对于记录，可变类通常声明一个 -mutableCopy 方法做可变的副本。但是，它不被声明的属性使用。如果你不想使用 retain ，你需要实现一个使用 -mutableCopy 的自定义setter。
 
First I read this article

I think I should use "copy" in my programe.
Problem is using NSMutableDictionary copy it will terminate.

* Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[__NSCFDictionary removeAllObjects]: mutating method sent to immutable object'

I have no idea about "mutating method sent to immutable object".
I didn't set NSDictionary to NSMutabledictionary pointer.

Here is my code






.h file
@interface Button : NSObject {

@private
    NSString*               gID;                                 
    NSString*               gBackColor;                          
    NSString*               gIconImage;                          
    int                     gIndex;                              
    BOOL                    gEnable;                            
    BOOL                    gVisible;
    NSString*               gText;

    NSMutableDictionary*    gEvents;


    BOOL                    gUseCircle;                 
}

@property (nonatomic,copy) NSString                 *ID;
@property (nonatomic,copy) NSString                 *BackColor;
@property (nonatomic,copy) NSString                 *IconImage;
@property int Index;
@property BOOL Enable;
@property BOOL Visible;
@property (nonatomic,copy) NSString                 *Text;
@property (nonatomic,getter=getEvents,retain) NSMutableDictionary       *Events;
@property BOOL UseCircle;

@end





.m file
@implementation Button
@synthesize ID = gID;
@synthesize BackColor = gBackColor;
@synthesize IconImage = gIconImage;
@synthesize Index = gIndex;
@synthesize Enable = gEnable;
@synthesize Visible = gVisible;
@synthesize Text = gText;
@synthesize Events = gEvents;
@synthesize UseCircle = gUseCircle;

-(NSMutableDictionary*) getEvents
{
    if (!gEvents) 
    {
        gEvents = [[NSMutableDictionary alloc] initWithCapacity:20];
    }
    return gEvents;
}

- (id) init
{
    self = [super init];
    if (self != nil) 
    {
        gID = @"";
        gBackColor = @"";
        gIconImage = @"";
        gIndex = 0;
        gText = @"";

        gUseCircle = NO;
    }
    return self;
}

- (void) dealloc
{
    [gID release];
    [gBackColor release];
    [gIconImage release];
    [gText release];

    [gEvents removeAllObjects];
    [gEvents release];
    gEvents = nil;

    [super dealloc];
}





And implement
tBtnXML.Events = [self SplitEvents:tNode];





SplitEvents function:
-(NSMutableDictionary*) SplitEvents:(NSDictionary*)pEvents
{
    NSMutableDictionary *tEvents = [[NSMutableDictionary alloc] initWithCapacity:5];
    // code blabla
    //.
    //.
    //.
    [tEvents setObject:tEvent forKey:[NSNumber numberWithInt:tEventName]];
    [tEvent release];



            return [tEvents autorelease];
}



But I chage  NSMutableDictionary* gEvents property from copy to retain , it execute normal.

Colud anyone tell me what's wrong with my code?

If my code is incorrect with dealloc,please tell me.

Thank you appriciate.













Yes, So I fixed my setter:
-(void) setEvents:(NSMutableDictionary*) pEvents
{
    NSMutableDictionary* tNewDict = [pEvents mutableCopy];
    [gEvents removeAllObjects];
    [gEvents release];
    gEvents = tNewDict;
}



This work with no error.

It helps me a lot.

But I can't vote up >"<~

So thank you Bavarious :)


解决方案
In general, mutable properties should be retain instead of copy. When you declare a property as being copy, the synthesised setter method sends -copy to the object that’s being assigned to the property. In the case of mutable objects (e.g. NSMutableDictionary), sending -copy to them makes an immutable copy, effectively creating an object of immutable type (e.g. NSDictionary) instead. 

So in:
tBtnXML.Events = [self SplitEvents:tNode];
the synthesised setter sends -copy to [self SplitEvents:tNode], thus creating an immutable copy of that dictionary (i.e., an NSDictionary instance), and assign it to gEvents. This is the cause of your error: gEvents is declared as NSMutableDictionary but points to an NSDictionary instead.

For the record, mutable classes usually declare a -mutableCopy method that does make a mutable copy. It is not used by declared properties, though. If you do not want to use retain, you need to implement a custom setter that uses -mutableCopy.

                        
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