NSArray與NSSet

NSArray：有序的集合，存儲的元素在一個整塊的內存中並按序排列；
NSSet：無序的集合，散列存儲。
讀developer.apple關於NSSet的解釋：You can use sets as an alternative to arrays when the order of elements isn’t important and performance in testing whether an object is contained in the set is a consideration—while arrays are ordered, testing for membership is slower than with sets.
就是說，如果搜索一個元素，NSSet的效率會比NSArray高。爲什麼呢？道理比較簡單：hash！NSSet中元素的存儲和訪問都是一個hash的過程。比如你要存儲元素A，一個hash算法直接就能直接找到A應該存儲的位置；同樣，當你要訪問A時，一個hash過程就能找到A存儲的位置。而對於NSArray，若想知道A到底在不在數組中，則需要一個一個元素比較，顯然效率沒了。

循環使用整個NSArray內的對象

循環使用整個NSArray內的對象是非常常用的了，而且最近我在研究究竟怎麼能方便的把NSArray存入Core Data，所以這更是必要了，看看如下的方法吧：

1，Objective-C 2.0法，最應該使用的

NSArray *aArray; //我們的Array，假設他已經初始化有內容了
 for(id innerObj in aArray) //id可以由其他對象類型替代
{
//也就是說, 在循環中的參數innerObj就是aArray中的對象
//由於NSArray中只能儲存對象，所以我們使用id作爲內涵對象的類型，其實就是個指針了
//而且如果NSArray中的內容不一致，id更不會出現衝突
}

2，C的老方法，不推薦，低性能

NSArray *aArray; //我們的Array，假設他已經初始化有內容了
 for(int i=0;i<[aArray count]; i++)
{
[[aArray objectAtIndex:i] 然後作你想作的事情]; //做愛 作的事情...
}

3, 用NSEnumerator（不知道怎麼翻譯阿….）

 NSEnumerator* myIterator = [myArray reverseObjectEnumerator];
 id anObject;
 while( anObject = [myIterator nextObject]) //每次讀取“逐讀器”的下一個對象
 {
     //anObject和剛纔的innerObj是一個意思，但是看看多了這麼多行
 }

三種集合類來收集cocoa對象（NSObject對象）：
NSArray 用於對象有序集合（相當於是數組）
NSSet 用於對象無序集合
NSDictionary用於鍵值映射
以上三種集合類是不可變的（一旦初始化後，就不能改變）

以下是對應的三種可變集合類(這三種可變集合類是對應上面三種集合類的子類)：
NSMutableArray
NSMutableSet
NSMutableDictionary

注：這些集合類只能收集cocoa對象（NSOjbect對象），如果想保存一些原始的C數據（例如，int, float, double, BOOL等），則需要將這些原始的C數據封裝成NSNumber類型的，NSNumber對象是cocoa對象，可以被保存在集合類中。

NSArray
Ordered collection of objects. Immutable. You cannot add or remove objects to it once it’s created.
Important methods:
+ (id)arrayWithObjects:(id)firstObject, ...;     // nil terminated
- (int)count;
- (id)objectAtIndex:(int)index;                     // NSString *s1=[[myarray objectAtIndex: 0];
- (void)makeObjectsPerformSelector:(SEL)aSelector;
- (NSArray *)sortedArrayUsingSelector:(SEL)aSelector;
- (id)lastObject; // returns nil if there are no objects in the array (convenient)
注：
類方法arrayWithObjects 可以創建an autoreleased NSArray of the items.例如
@implementation MyObject
- (NSArray *)coolCats {
return [NSArray arrayWithObjects:@“Steve”, @“Ankush”, @“Sean”, nil];
}
@end
Other convenient create with methods (all return autoreleased objects):
[NSString stringWithFormat:@“Meaning of %@ is %d”, @“life”, 42];
[NSDictionary dictionaryWithObjectsAndKeys:ankush, @“TA”, janestudent, @“Student”, nil];
[NSArray arrayWithContentsOfFile:(NSString *)path];
-----創建數組 -----
    //NSArray *array = [[NSArray alloc] initWithObjects:
    @"One",@"Two",@"Three",@"Four",nil];

self.dataArray = array;
[array release];

//- (unsigned) Count;數組所包含對象個數；
NSLog(@"self.dataArray cound:%d",[self.dataArray count]);

//- (id) objectAtIndex: (unsigned int) index;獲取指定索引處的對象;
NSLog(@"self.dataArray cound 2:%@",[self.dataArray objectAtIndex:2]);

------ 從一個數組拷貝數據到另一數組(可變數級) -------

    //arrayWithArray:
    //NSArray *array1 = [[NSArray alloc] init];
    NSMutableArray *MutableArray = [[NSMutableArray alloc] init];
    NSArray *array = [NSArray arrayWithObjects:
                      @"a",@"b",@"c",nil];
    NSLog(@"array:%@",array);
    MutableArray = [NSMutableArray arrayWithArray:array];
    NSLog(@"MutableArray:%@",MutableArray);

array1 = [NSArray arrayWithArray:array];
NSLog(@"array1:%@",array1);

//Copy

    //id obj;
    NSMutableArray *newArray = [[NSMutableArray alloc] init];
    NSArray *oldArray = [NSArray arrayWithObjects:
                         @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];

    NSLog(@"oldArray:%@",oldArray);
    for(int i = 0; i < [oldArray count]; i++)
    {
        obj = [[oldArray objectAtIndex:i] copy];
        [newArray addObject: obj];
    }
    //
    NSLog(@"newArray:%@", newArray);
    [newArray release];

//快速枚舉
    //NSMutableArray *newArray = [[NSMutableArray alloc] init];
    NSArray *oldArray = [NSArray arrayWithObjects:
                         @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
    NSLog(@"oldArray:%@",oldArray);

    for(id obj in oldArray)
    {
        [newArray addObject: obj];
    }
    //
    NSLog(@"newArray:%@", newArray);
    [newArray release];

//Deep copy

    //NSMutableArray *newArray = [[NSMutableArray alloc] init];
    NSArray *oldArray = [NSArray arrayWithObjects:
                         @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
    NSLog(@"oldArray:%@",oldArray);
    newArray = (NSMutableArray*)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (CFPropertyListRef)oldArray, kCFPropertyListMutableContainers);
    NSLog(@"newArray:%@", newArray);
    [newArray release];

//Copy and sort

//NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects:

NSMutableArray
Mutable version of NSArray.
- (void)addObject:(id)anObject;
- (void)insertObject:(id)anObject atIndex:(int)index;
- (void)removeObjectAtIndex:(int)index;
- (void)removeAllObjects;

-----給數組分配容量-----
//NSArray *array;
array = [NSMutableArray arrayWithCapacity:20];

-----在數組末尾添加對象-----
    //- (void) addObject: (id) anObject;
    //NSMutableArray *array = [NSMutableArray arrayWithObjects:@"One",@"Two",@"Three",nil];
    [array addObject:@"Four"];
    NSLog(@"array:%@",array);

-----刪除數組中指定索引處對象-----
    //-(void) removeObjectAtIndex: (unsigned) index;
    //NSMutableArray *array = [NSMutableArray arrayWithObjects:@"One",@"Two",@"Three",nil];
    [array removeObjectAtIndex:1];
    NSLog(@"array:%@",array);

----- 數組枚舉-----
//1、- (NSEnumerator *)objectEnumerator;  //從前向後
    //NSMutableArray *array = [NSMutableArray arrayWithObjects:@"One",@"Two",@"Three",nil];
    NSEnumerator *enumerator;
    enumerator = [array objectEnumerator];

    id thingie;
    while (thingie = [enumerator nextObject]) {
        NSLog(@"thingie:%@",thingie);
    }
//2、- (NSEnumerator *)reverseObjectEnumerator;  //從後向前
    //NSMutableArray *array = [NSMutableArray arrayWithObjects:
    @"One",@"Two",@"Three",nil];
    NSEnumerator *enumerator;
    enumerator = [array reverseObjectEnumerator];

    id object;
    while (object = [enumerator nextObject]) {
        NSLog(@"object:%@",object);
    }
//3、快速枚舉
    //NSMutableArray *array = [NSMutableArray arrayWithObjects:
    @"One",@"Two",@"Three",nil];
    for(NSString *string in array)
    {
        NSLog(@"string:%@",string);
    }

----- NSValue（對任何對象進行包裝）-----
//將NSRect放入NSArray中
    NSMutableArray *array = [[NSMutableArray alloc] init];
    NSValue *value;
    CGRect rect = CGRectMake(0, 0, 320, 480);
    value = [NSValue valueWithBytes:&rect objCType:@encode(CGRect)];
    [array addObject:value];
    NSLog(@"array:%@",array);
//從Array中提取
    value = [array objectAtIndex:0];
    [value getValue:&rect];
    NSLog(@"value:%@",value);

----★使用NSMutableArray要防止內存泄露★------
NSObject* p1 = [[NSObject alloc] init];
NSObject* p2 = [[NSObject alloc] init];
NSMutableArray* objectsArray = [[NSMutableArray alloc] init];

[objectsArray addObject:p1];
NSLog(@"p1 count:%d", [p1 retainCount]);//輸出 2，也就是執行追加對象後，對象的計數器也被加1
//[p1 release];
//NSLog(@"p1 count:%d", [p1 retainCount]);

//同樣做數組替換時
[objectsArray replaceObjectAtIndex:0 withObject:p2];
NSLog(@"p2 count:%d", [p2 retainCount]);//輸出 2，同樣也是2
NSLog(@"p1 count:%d", [p1 retainCount]);//輸出 1，對象p1仍然存在
//[p2 release];
//NSLog(@"p2 count:%d", [p2 retainCount]);

//執行清空數組
[objectsArray removeAllObjects];
NSLog(@"p2 count:%d", [p2 retainCount]);//輸出 1，對象p2仍然存在
//[p2 release];

由此可知，每次執行上面的數組操作後，要執行對象release，如上面註釋中的語句，才能保證內存不泄露。

NSSet
Unordered collection of objects.
Immutable. You cannot add or remove objects to it once it’s created.
Important methods:
+ setWithObjects:(id)firstObj, ...; // nil terminated

- (int)count;
- (BOOL)containsObject:(id)anObject;
- (id)anyObject;
- (void)makeObjectsPerformSelector:(SEL)aSelector;
- (id)member:(id)anObject; // uses isEqual: and returns a matching object (if any)

NSMutableSet
Mutable version of NSSet.
+ (NSMutableSet *)set;

- (void)addObject:(id)anObject;
- (void)removeObject:(id)anObject;

- (void)removeAllObjects;
- (void)unionSet:(NSSet *)otherSet;
- (void)minusSet:(NSSet *)otherSet;
- (void)intersectSet:(NSSet *)otherSet;

NSDictionary
key-value, key-value, ..... 一系列鍵值對。

key（鍵）在整個dictionary是唯一的，通過key可以查詢其對應的一個或多個value（值）。

Hash table. Look up objects using a key to get a value.
Immutable. You cannot add or remove objects to it once it’s created.
Keys are objects which must implement. Keys are usually NSString objects.
- (NSUInteger)hash & - (BOOL)isEqual:(NSObject *)obj
Important methods:
+ dictionaryWithObjectsAndKeys: (id)firstObject, ...;

- (int)count;
- (id)objectForKey:(id)key;
- (NSArray *)allKeys;
- (NSArray *)allValues;

-----創建字典 -----
//- (id) initWithObjectsAndKeys;

    //NSDictionary *dictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"One",@"1",@"Two",@"2",@"Three",@"3",nil];
    NSString *string = [dictionary objectForKey:@"One"];
    NSLog(@"string:%@",string);
    NSLog(@"dictionary:%@",dictionary);
    [dictionary release];

NSMutableDictionary
Mutable version of NSDictionary.
+ (NSMutableDictionary *)dictionary;

- (void)setObject:(id)anObject forKey:(id)key;
- (void)removeObjectForKey:(id)key;

- (void)removeAllObjects;
- (void)addEntriesFromDictionary:(NSDictionary *)otherDictionary;

-----創建可變字典 -----
//創建
    NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
//添加字典
    [dictionary setObject:@"One" forKey:@"1"];
    [dictionary setObject:@"Two" forKey:@"2"];
    [dictionary setObject:@"Three" forKey:@"3"];
    [dictionary setObject:@"Four" forKey:@"4"];
    NSLog(@"dictionary:%@",dictionary);
//刪除指定的字典
    [dictionary removeObjectForKey:@"3"];
    NSLog(@"dictionary:%@",dictionary);

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