好程序员学习笔记--数组问题
line-height:24px">NSArray用于对象有序集合(数组)
NSSet用于对象无序集合(集合)
NSDictionary用于键值映射(字典)
以上三种集合类是不可变的(一旦初始化后,就不能改变)
以下是对应的三种可变集合类(这三种可变集合类是对应上面三种集合类的子类):
NSMutableArray
NSMutableSet
NSMutableDictionary
注:这些集合类只能收集cocoa对象(NSOjbect对象),如果想保存一些原始的C数据(例如,int, float, double, BOOL等),则需要将这些原始的C数据封装成NSNumber 类型的,NSNumber对象是cocoa对象,可以被保存在集合类中。
===================NSArray====================
Ordered collection of objects.Immutable(you cannot add or remove objects to it once it’s created)
Important methods:
+ (id)arrayWithObjects:(id)firstObject, ...;//nilterminated
- (int)count;
// 得到array中的对象个数
- (id)objectAtIndex:(int)index; // 得到索引为i的对象
- (BOOL)containsObject:(id)anObject; // 当anObject出现在array中,则返回yes(实际是通过isEqual:方法来判断)
- (unsigned)indexOfObject:(id)anObject;
// 查找array中的anObject,并返回其最小索引值。没找到返回NSNotFound.
- (void)makeObjectsPerformSelector:(SEL)aSelector;
- (NSArray *)sortedArrayUsingSelector:(SEL)aSelector;
- (id)lastObject;
// 得到array中最后一个对象。如果array中没有任何对象存在,则返回nil
注:
类方法arrayWithObjects可以创建anautoreleasedNSArray 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];
-----创建数组-----
NSArray *array = [[NSArray alloc]
initWithObjects:@One,@Two,@Three,@Four,nil];
self.dataArray = array;
[array release];
NSLog(@self.dataArray count is:%d,[self.dataArray count]);
NSLog(@self.dataArray index 2 is:%@,[self.dataArray objectAtIndex:2]);
------从一个数组拷贝数据到另一数组(可变数级)-------
//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];
===================NSMutableArray==================== Mutable version of NSArray.
- (void)addObject:(id)anObject;// 在array最后添加anObject, 添加nil是非法的.
- (void)addObjectsFromArray:(NSArray *)otherArray;//在array最后把otherArray中的对象依次添加进去。
- (void)insertObject:(id)anObject atIndex:(int)index;//在索引index处插入anObject, 若index被占用,会把之后的object向后移。
- (void)removeObjectAtIndex:(int)index; //删除index处的对象,后面的对象依次向前移。
- (void)removeObject:(id)anObject; // 删除所有和anObject相等的对象,同样使用isEqual:作为相等比较方法.
- (void)removeAllObjects;
注:我们不能把nil加到array中。但有时候我们真想给array加一个空的对象,可以使用NSNull来做这件事。如:
[myArray addObject:[NSNull null]];
-----给数组分配容量-----
//NSArray *array;
array = [NSMutableArrayarrayWithCapacity:20];
-----在数组末尾添加对象-----
//- (void) addObject: (id) anObject;
//NSMutableArray *array = [NSMutableArrayarrayWithObjects:@One,@Two,@Three,nil];
[arrayaddObject:@Four];
NSLog(@array:%@,array);
-----删除数组中指定索引处对象-----
//-(void) removeObjectAtIndex: (unsigned) index;
//NSMutableArray *array = [NSMutableArray arrayWithObjects:@One,@Two,@Three,nil];
[arrayremoveObjectAtIndex:1];
NSLog(@array:%@,array);
-----数组枚举-----
//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);
}
-----NSValue(对任何对象进行包装)-----
//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);
----★使用NSMutableArray要防止内存泄露★------
NSObject* p1 = [[NSObject alloc]
init];
NSObject* p2 = [[NSObject alloc]
init];
NSMutableArray* objectsArray = [[NSMutableArray alloc]
init];
[objectsArray addObject:p1];
NSLog(@p1 count:%d, [p1 retainCount]);//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2
NSLog(@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];
由此可知,每次执行上面的数组操作后,要执行对象release,如上面注释中的语句,才能保证内存不泄露。
NSSet
Unordered collection of objects.
Immutable. You cannot add or remove objects to it once it’s created.
Important methods:
+ setWithObjects:(id)firstObj, ...; //nilterminated
- (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
一个dictionary就是key-value对的集合。key是字符串(NSString),value是对象指针。
key在整个dictionary是唯一的。通过方法objectForKey:来获得对应于某个key的一个或多个value(值)。
NSDictionary在创建时,其中所有的key和对应的value都存在了。你可以访问其内容,但不可以修改。
dictionary使用hash表来实现,所以查找速度很快。
- (NSUInteger)hash - (BOOL)isEqual:(NSObject *)obj
Important methods:
+ dictionaryWithObjectsAndKeys: (id)firstObject, ...;
- (int)count;// 返回有多少对key-value
- (id)objectForKey:(id)key; //返回和key相关联的value。
如果没有和key相关联的value,则返回nil。
- (NSArray *)allKeys; // 返回一个包含所有key的array
- (NSArray *)allValues;
- NSEnumerator *)keyEnumerator; //这个方法是从一个dictionary 中得到一个key 的迭代器.
Enumerators也就是iterators 或enumerations.我们可以使用它来一步一步迭代出集合中的所有成员.
下面是我们可能使用它来列举所有的key- ‐vaule 对
NSEnumerator *e = [myDict keyEnumerator];
for (NSString *s in e) {
NSLog(@key is %@, value is %@, s, [myDict objectForKey:s]);
}
注:NSArray 也有一个类似的方法得到array 的成员迭代器 : objectEnumerator -----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];
NSMutableDictionary
Mutable version of NSDictionary.
NSMutableDictionary是NSDictionary的子类。创建后,允许用户添加和删除key 和value。
+ (NSMutableDictionary *)dictionary; // 创建一个空的dictionary
- (void)setObject:(id)anObjectforKey:(id)key; // 使用key和anObject组成一条记录添加到dictionary中
// 如果key已存在,则会先移除旧的key-value,然后再添加新的key-value。
- (void)removeObjectForKey:(id)key;
// 从dictionary中删除一条记录,key以及和它对应的value
- (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);