NSArray与NSSet .
NSArray与NSSet
NSArray：有序的集合，存储的元素在一个整块的内存中并按序排列；
NSSet：无序的集合，散列存储。
读developer.apple关于NSSet的解释：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.
就是说，如果搜索一个元素，NSSet的效率会比NSArray高。为什么呢？道理比较简单：hash！NSSet中元素的存储和访问都是一个hash的过程。比如你要存储元素A，一个hash算法直接就能直接找到A应该存储的位置；同样，当你要访问A时，一个hash过程就能找到A存储的位置。而对于NSArray，若想知道A到底在不在数组中，则需要一个一个元素比较，显然效率没了。
循环使用整个NSArray内的对象
循环使用整个NSArray内的对象是非常常用的了，而且最近我在研究究竟怎么能方便的把NSArray存入Core Data，所以这更是必要了，看看如下的方法吧：
1，Objective-C 2.0法，最应该使用的
NSArray *aArray; //我们的Array，假设他已经初始化有内容了 for(id innerObj in aArray) //id可以由其他对象类型替代{//也就是说, 在循环中的参数innerObj就是aArray中的对象//由于NSArray中只能储存对象，所以我们使用id作为内涵对象的类型，其实就是个指针了//而且如果NSArray中的内容不一致，id更不会出现冲突}for(int i=0;i<[aArray count]; i++){[[aArray objectAtIndex:i] 然后作你想作的事情]; //做爱 作的事情...}NSEnumerator* myIterator = [myArray reverseObjectEnumerator]; id anObject; while( anObject = [myIterator nextObject]) //每次读取“逐读器”的下一个对象 { //anObject和刚才的innerObj是一个意思，但是看看多了这么多行 }+ (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：类方法arrayWithObjects 可以创建an autoreleased NSArray of the items.例如@implementation MyObject- (NSArray *)coolCats {return [NSArray arrayWithObjects:@“Steve”, @“Ankush”, @“Sean”, nil];}@endOther 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];//NSArray *array = [[NSArray alloc] initWithObjects: @"One",@"Two",@"Three",@"Four",nil]; self.dataArray = array; [array release]; //- (unsigned) Count;数组所包含对象个数； NSLog(@"self.dataArray cound:%d",[self.dataArray count]); //- (id) objectAtIndex: (unsigned int) index;获取指定索引处的对象; NSLog(@"self.dataArray cound 2:%@",[self.dataArray objectAtIndex:2]);
//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];//快速枚举 //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:- (void)addObject:(id)anObject;- (void)insertObject:(id)anObject atIndex:(int)index;- (void)removeObjectAtIndex:(int)index;- (void)removeAllObjects;
//NSArray *array; array = [NSMutableArray arrayWithCapacity:20];
//- (void) addObject: (id) anObject; //NSMutableArray *array = [NSMutableArray arrayWithObjects:@"One",@"Two",@"Three",nil]; [array addObject:@"Four"]; NSLog(@"array:%@",array);
//-(void) removeObjectAtIndex: (unsigned) index; //NSMutableArray *array = [NSMutableArray arrayWithObjects:@"One",@"Two",@"Three",nil]; [array removeObjectAtIndex:1]; NSLog(@"array:%@",array);
//1、- (NSEnumerator *)objectEnumerator; //从前向后 //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; //从后向前 //NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil]; NSEnumerator *enumerator; enumerator = [array reverseObjectEnumerator]; id object; while (object = [enumerator nextObject]) { NSLog(@"object:%@",object); }//3、快速枚举 //NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil]; for(NSString *string in array) { NSLog(@"string:%@",string); }//将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);//从Array中 提取 value = [array objectAtIndex:0]; [value getValue:&rect]; NSLog(@"value:%@",value);
NSObject* p1 = [[NSObject alloc] init];NSObject* p2 = [[NSObject alloc] init];NSMutableArray* objectsArray = [[NSMutableArray alloc] init];[objectsArray addObject:p1];NSLog(@"p1 count:%d", [p1 retainCount]);//输出 2，也就是执行追加对象后，对象的计数器也被加1//[p1 release];//NSLog(@"p1 count:%d", [p1 retainCount]);//同样做数组替换时[objectsArray replaceObjectAtIndex:0 withObject:p2];NSLog(@"p2 count:%d", [p2 retainCount]);//输出 2，同样也是2NSLog(@"p1 count:%d", [p1 retainCount]);//输出 1，对象p1仍然存在//[p2 release];//NSLog(@"p2 count:%d", [p2 retainCount]);//执行清空数组[objectsArray removeAllObjects];NSLog(@"p2 count:%d", [p2 retainCount]);//输出 1，对象p2仍然存在//[p2 release];
+ 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 *)set;- (void)addObject:(id)anObject;- (void)removeObject:(id)anObject;- (void)removeAllObjects;- (void)unionSet:(NSSet *)otherSet;- (void)minusSet:(NSSet *)otherSet;- (void)intersectSet:(NSSet *)otherSet;
- (NSUInteger)hash & - (BOOL)isEqual:(NSObject *)objImportant methods:+ dictionaryWithObjectsAndKeys: (id)firstObject, ...;- (int)count;- (id)objectForKey:(id)key;- (NSArray *)allKeys;- (NSArray *)allValues; -----创建字典 ----- //- (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];NSMutableDictionaryMutable version of NSDictionary.+ (NSMutableDictionary *)dictionary;- (void)setObject:(id)anObject forKey:(id)key;- (void)removeObjectForKey:(id)key;- (void)removeAllObjects;- (void)addEntriesFromDictionary:(NSDictionary *)otherDictionary;-----创建可变字典 -----
//创建 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);//删除指定的字典 [dictionary removeObjectForKey:@"3"]; NSLog(@"dictionary:%@",dictionary);