blocks|key|1352670|text|没有真正的队列集合类，但是NSMutableArray可以有效地用于同样的事情。为了方便起见，您可以定义一个category来添加弹出/推送方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1352671|entityMap|0|LINK|mutability|MUTABLE|url|http://macdevelopertips.com/objective-c/objective-c-categories.html^0|1I|8|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

There's no real queue collections class, but NSMutableArray can be used for effectively the same thing. You can define a <a href="http://macdevelopertips.com/objective-c/objective-c-categories.html" rel="nofollow noreferrer">category</a> to add pop/push methods as a convenience if you want.

blocks|key|1568106|text|可以，使用NSMutableArray。NSMutableArray实际上是implemented形式的2-3树；您通常不需要关心在任意索引的NSMutableArray中添加或删除对象的性能特征。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1568107|entityMap|0|LINK|mutability|MUTABLE|url|http://www.opensource.apple.com/darwinsource/10.5.6/CF-476.17/CFStorage.c^0|12|B|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Yes, use NSMutableArray. NSMutableArray is actually <a href="http://www.opensource.apple.com/darwinsource/10.5.6/CF-476.17/CFStorage.c" rel="noreferrer">implemented</a> as 2-3 tree; you typically need not concern yourself with the performance characteristics of adding or removing objects from NSMutableArray at arbitrary indices.

blocks|key|1352933|text|re:Wolfcow+--这里是Wolfcow的dequeue方法的一个正确的实现|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1352934|-+(id)dequeue+{
++++if+([self+count]+==+0)+{
++++++++return+nil;
++++}
++++id+queueObject+=+[[[self+objectAtIndex:0]+retain]+autorelease];
++++[self+removeObjectAtIndex:0];
++++return+queueObject;
}|code-block|syntax|javascript|1352935|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

re:Wolfcow -- Here is a corrected implementation of Wolfcow's dequeue method

<pre><code>- (id)dequeue {
 if ([self count] == 0) {
 return nil;
 }
 id queueObject = [[[self objectAtIndex:0] retain] autorelease];
 [self removeObjectAtIndex:0];
 return queueObject;
}
</code></pre>

blocks|key|1353103|text|在NSMutableArray上使用类别的解决方案不是真正的队列，因为NSMutableArray公开的操作是队列的超集。例如，您不应该被允许从队列中间删除项(就像那些类别解决方案仍然允许您做的那样)。最好是封装功能，这是面向对象设计的主要原则。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1353104|StdQueue.h|1353105|#import+<Foundation/Foundation.h>

@interface+StdQueue+:+NSObject

@property(nonatomic,+readonly)+BOOL+empty;
@property(nonatomic,+readonly)+NSUInteger+size;
@property(nonatomic,+readonly)+id+front;
@property(nonatomic,+readonly)+id+back;

-+(void)enqueue:(id)object;
-+(id)dequeue;

@end|code-block|syntax|javascript|1353106|StdQueue.m|1353107|#import+"StdQueue.h"

@interface+StdQueue+()

@property(nonatomic,+strong)+NSMutableArray*+storage;

@end

@implementation+StdQueue

#pragma+mark+NSObject

-+(id)init
{
++++if+(self+=+[super+init])+{
++++++++_storage+=+[NSMutableArray+array];
++++}
++++return+self;
}

#pragma+mark+StdQueue

-+(BOOL)empty
{
++++return+self.storage.count+==+0;
}

-+(NSUInteger)size
{
++++return+self.storage.count;
}

-+(id)front
{
++++return+self.storage.firstObject;
}

-+(id)back
{
++++return+self.storage.lastObject;
}

-+(void)enqueue:(id)object
{
++++[self.storage+addObject:object];
}

-+(id)dequeue
{
++++id+firstObject+=+nil;
++++if+(!self.empty)+{
++++++++firstObject++=+self.storage.firstObject;
++++++++[self.storage+removeObjectAtIndex:0];
++++}
++++return+firstObject;
}

@end|1353108|entityMap^0|1|E|Z|E|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Z|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|R|$]]

The solutions that use a category on <code>NSMutableArray</code> are not true queues, because <code>NSMutableArray</code> exposes operations that are a superset of queues. For example, you should not be allowed to remove an item from the middle of a queue (as those category solutions still let you do). It is best to encapsulate functionality, a major principle of object oriented design.

StdQueue.h

<pre><code>#import &lt;Foundation/Foundation.h&gt;

@interface StdQueue : NSObject

@property(nonatomic, readonly) BOOL empty;
@property(nonatomic, readonly) NSUInteger size;
@property(nonatomic, readonly) id front;
@property(nonatomic, readonly) id back;

- (void)enqueue:(id)object;
- (id)dequeue;

@end
</code></pre>

StdQueue.m

<pre><code>#import "StdQueue.h"

@interface StdQueue ()

@property(nonatomic, strong) NSMutableArray* storage;

@end

@implementation StdQueue

#pragma mark NSObject

- (id)init
{
 if (self = [super init]) {
 _storage = [NSMutableArray array];
 }
 return self;
}

#pragma mark StdQueue

- (BOOL)empty
{
 return self.storage.count == 0;
}

- (NSUInteger)size
{
 return self.storage.count;
}

- (id)front
{
 return self.storage.firstObject;
}

- (id)back
{
 return self.storage.lastObject;
}

- (void)enqueue:(id)object
{
 [self.storage addObject:object];
}

- (id)dequeue
{
 id firstObject = nil;
 if (!self.empty) {
 firstObject = self.storage.firstObject;
 [self.storage removeObjectAtIndex:0];
 }
 return firstObject;
}

@end
</code></pre>

blocks|key|1568285|text|这是我的实现，希望它能有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1568286|是一种极简主义，所以你必须通过在pop保存新的头部并丢弃旧的头部来保持头部的轨迹|1568287|@interface+Queue+:+NSObject+{
++++id+_data;
++++Queue+*tail;
}

-(id)+initWithData:(id)+data;
-(id)+getData;

-(Queue*)+pop;
-(void)+push:(id)+data;

@end

#import+"Queue.h"

@implementation+Queue

-(id)+initWithData:(id)+data+{
++++if+(self=[super+init])+{
++++++++_data+=+data;
++++++++[_data+retain];
++++}
++++return+self;
}
-(id)+getData+{
++++return+_data;
}

-(Queue*)+pop+{
++++return+tail;
}
-(void)+push:(id)+data{
++++if+(tail)+{
++++++++[tail+push:data];
++++}+else+{
++++++++tail+=+[[Queue+alloc]initWithData:data];
++++}
}

-(void)+dealloc+{
++++if+(_data)+{
++++++++[_data+release];
++++}
++++[super+release];
}

@end|code-block|syntax|javascript|1568288|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

this is my implementation, hope it helps.

Is kind of minimalistic, so you must keep the track of the head by saving the new head at pop and discarding the old head

<pre><code>@interface Queue : NSObject {
 id _data;
 Queue *tail;
}

-(id) initWithData:(id) data;
-(id) getData;

-(Queue*) pop;
-(void) push:(id) data;

@end

#import "Queue.h"

@implementation Queue

-(id) initWithData:(id) data {
 if (self=[super init]) {
 _data = data;
 [_data retain];
 }
 return self;
}
-(id) getData {
 return _data;
}

-(Queue*) pop {
 return tail;
}
-(void) push:(id) data{
 if (tail) {
 [tail push:data];
 } else {
 tail = [[Queue alloc]initWithData:data];
 }
}

-(void) dealloc {
 if (_data) {
 [_data release];
 }
 [super release];
}

@end
</code></pre>

blocks|key|1568185|text|有什么特殊的原因不能直接使用STL队列吗？Objective+C%2B%2B是C%2B%2B的超集(只需使用.mm而不是.m作为扩展，以便使用Objective+C%2B%2B而不是Objective+C)。然后，您可以使用STL或任何其他C%2B%2B代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1568186|在Objective+C对象中使用STL队列/向量/列表等的一个问题是，它们通常不支持保留/释放/自动释放内存管理。这很容易通过C%2B%2B智能指针容器类解决，该类在构造时保留其Objective+C对象，并在被销毁时释放它。根据您放在STL队列中的内容，这通常是不必要的。|1568187|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Is there some particular reason you cannot just use the STL queue? Objective C++ is a superset of C++ (just use .mm as the extension instead of .m to use Objective C++ instead of Objective C). Then you can use the STL or any other C++ code.

One issue of using the STL queue/vector/list etc with Objective C objects is that they do not typically support retain/release/autorelease memory management. This is easily worked around with a C++ Smart Pointer container class which retains its Objective C object when constructed and releases it when destroyed. Depending on what you are putting in the STL queue this is often not necessary.

blocks|key|1568030|text|使用NSMutableArray。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1568031|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I want to use a queue data structure in my Objective-C program. In C++ I'd use the STL queue. What is the equivalent data structure in Objective-C? How do I push/pop items?

How do I make and use a Queue in Objective-C?

数据结构

内存管理

Objective-C

容器

我想在Objective-C程序中使用队列数据结构。在C++中，我会使用STL队列。Objective-C中等价的数据结构是什么？如何推送/弹出项目？

问如何在Objective-C中创建和使用队列？
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