字典用于保存具有映射關(guān)系數(shù)據(jù)的集合
一個(gè)key—value對(duì)認(rèn)為是一個(gè)條目（entry），字典是存儲(chǔ)key—value對(duì)的容器
與數(shù)組不同，字典靠key存取元素
key不能重復(fù)，value必須是對(duì)象
鍵值對(duì)在字典中是無(wú)序存儲(chǔ)的
字典分：不可變字典（NSDictionary）和可變字典（NSMutableDictionary）
不可變字典一旦創(chuàng)建，鍵值對(duì)就不可更改，不可添加，不可刪除，僅能讀取key或者value
常用方法有：
1、創(chuàng)建字典對(duì)象
2、獲取所有key值，獲取所有value值
3、通過(guò)key值查詢value
1、常見(jiàn)字典的常用方法
在創(chuàng)建字典對(duì)象時(shí)需要賦值鍵值對(duì)，但是順序?yàn)椋褐担I，（值在前鍵在后的形式）
NSDictionary *dic1 = [[NSDictionary alloc] initWithObjectsAndKeys:@"Duke",@"name",@33,@"age",@"男",@"gender", nil];
NSLog(@"%@",dic1);
NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"Duke",@"name",@33,@"age",@"男",@"gender", nil];
NSLog(@"%@",dic2);
NSArray *keys = @[@"name",@"age",@"gender"];
NSArray *values = @[@"Duke",@33,@"male"];
字典的語(yǔ)法糖形式
鍵值對(duì)之間以逗號(hào)隔開，鍵和值之間以冒號(hào)隔開
NSDictionary *dic5 = @{@"name" : @"Duke",@"age" : @33,@"gender" : @"male"};
NSLog(@"%@",dic5);
創(chuàng)建字典對(duì)象時(shí)兩個(gè)數(shù)組元素個(gè)數(shù)必須一致
NSDictionary *dic3 = [[NSDictionary alloc] initWithObjects:values forKeys:keys];
NSLog(@"%@",dic3);
NSDictionary *dic4 = [NSDictionary dictionaryWithObjects:values forKeys:keys];
NSLog(@"%@",dic4);
通過(guò)count方法獲取字典中鍵值對(duì)的個(gè)數(shù)
NSInteger count = [dic4 count];
NSLog(@"%ld",count);
獲取字典中所有的鍵
NSArray *allKeys = [dic4 allKeys];
NSLog(@"%@",allKeys);
獲取字典中所有的值組成的值
NSArray *allValues = [dic4 allValues];
NSLog(@"%@",allValues);
通過(guò)指定的鍵獲取其在字典中對(duì)應(yīng)的值
id object = [dic4 objectForKey:@"age"];
NSLog(@"%@",object);
for (int i = 0; i < count; i++) {
id key = [allKeys objectAtIndex:i];
根據(jù)當(dāng)前遍歷得到的key去獲取對(duì)應(yīng)的value
id value = [dic4 objectForKey:key];
NSString *result = [value isKindOfClass:[NSString class]] ? @"YES" : @"NO";
NSLog(@"%@:%@-->%@",key,value,result);
}
NSMutableDictionary可變字典
可變NSMutableDictionary是NSDictionary的子類，擁有所有NSDictionary的方法
常用方法有：
1、創(chuàng)建字典對(duì)象
2、添加鍵值對(duì)
3、修改key對(duì)應(yīng)的value
4、刪除鍵值對(duì)
5、通過(guò)fou循環(huán)遍歷所有鍵值對(duì)
NSMutableDictionary可變字典對(duì)象的創(chuàng)建
NSMutableDictionary *dic6 = [[NSMutableDictionary alloc] initWithDictionary:dic5];
NSLog(@"%@",dic6);
NSMutableDictionary *dic7 = [NSMutableDictionary dictionaryWithDictionary:dic5];
NSLog(@"%@",dic7);
NSMutableDictionary *dic8 = [[NSMutableDictionary alloc] init];
NSLog(@"%@",dic8);
NSMutableDictionary *dic9 = [NSMutableDictionary dictionary];
NSLog(@"%@",dic9);
增加鍵值對(duì)
[dic9 setObject:@"Duke" forKey:@"name"];
[dic9 setObject:@"male" forKey:@"gender"];
[dic9 setObject:@33 forKey:@"age"];
NSLog(@"%@",dic9);
修改已有鍵對(duì)應(yīng)的值
如果鍵不存在，則為添加鍵值對(duì)，如果鍵存在，則為修改已有鍵對(duì)應(yīng)的值
[dic9 setObject:@34 forKey:@"age"];
NSLog(@"%@",dic9);
根據(jù)指定鍵去刪除對(duì)應(yīng)的鍵值對(duì)
[dic9 removeObjectForKey:@"age"];
NSLog(@"%@",dic9);
刪除所有的鍵值對(duì)
[dic9 removeAllObjects];
NSLog(@"%@",dic9);
OC中的集合（NSSet）與數(shù)學(xué)中的集合一樣，集合中的元素具有唯一性、存儲(chǔ)單元的元素是無(wú)序的、存儲(chǔ)元素必須是對(duì)象類型
OC中用Set表示集合，分為NSSet和NSMutableSet
NSSet對(duì)象的創(chuàng)建 無(wú)序性，互異性
NSSet的常用方法
1、創(chuàng)建集合對(duì)象
2、獲取元素個(gè)數(shù)
3、獲取集合中的某個(gè)元素
4、判斷集合中是否包含某個(gè)對(duì)象
創(chuàng)建集合對(duì)象
NSSet *set1 = [[NSSet alloc] initWithObjects:@"1",@"2",@"2",@"3", nil];
NSLog(@"%@",set1);
NSSet *set2 = [NSSet setWithObjects:@"3",@"2",@"1", nil];
NSLog(@"%@",set2);
用數(shù)組對(duì)象來(lái)創(chuàng)建集合對(duì)象
可以通過(guò)這種方法過(guò)濾掉數(shù)組中重復(fù)的元素對(duì)象
NSArray *array = @[@1,@2,@3,@2,@3];
NSSet *set3 = [[NSSet alloc] initWithArray:array];
NSSet *set4 = [NSSet setWithArray:array];
NSLog(@"%@",set3);
NSLog(@"%@",set4);
獲取集合中對(duì)象的個(gè)數(shù)
NSInteger count2 = [set4 count];
NSLog(@"%ld",count2);
獲取集合中的對(duì)象
id object1 = [set4 anyObject];
NSLog(@"%@",object1);
判斷一個(gè)給定的對(duì)象是否包含在指定的集合中
NSString *result1 = [set4 containsObject:@3] ? @"YES" : @"NO";
NSLog(@"%@is contained in set %@",@3,result1);
NSMutableSet的常用方法
1、創(chuàng)建集合對(duì)象
2、添加元素
3、刪除元素
創(chuàng)建NSMutableset對(duì)象
NSMutableSet *mutableSet1 = [[NSMutableSet alloc] init];
NSLog(@"%@",mutableSet1);
NSMutableSet *mutableSet2 = [NSMutableSet set];
NSLog(@"%@",mutableSet2);
通過(guò)不可變對(duì)象創(chuàng)建
NSMutableSet *mutableSet3 = [[NSMutableSet alloc] initWithSet:set1];
NSLog(@"%@",mutableSet3);
NSMutableSet *mutableSet4 = [NSMutableSet setWithSet:set1];
NSLog(@"%@",mutableSet4);
添加集合元素
[mutableSet4 addObject:@4];
NSLog(@"%@",mutableSet4);
刪除單個(gè)集合
[mutableSet4 removeObject:@"3"];
NSLog(@"%@",mutableSet4);
刪除所有元素
[mutableSet4 removeAllObjects];
NSLog(@"%@",mutableSet4);
NSCountedSet
NSCountedSet是NSMutableString的子類
能記錄元素的重復(fù)次數(shù)
在set的基礎(chǔ)上添加了計(jì)數(shù)功能
NSCountedSet記錄添加進(jìn)去的集合對(duì)象出現(xiàn)的次數(shù)
NSCountedSet *countedSet = [NSCountedSet set];
[countedSet addObject:@1];
[countedSet addObject:@2];
[countedSet addObject:@2];
NSLog(@"%@",countedSet);
單獨(dú)獲取某個(gè)對(duì)象在集合中出現(xiàn)過(guò)多少次
NSInteger countOfObjec = [countedSet countForObject:@1];
NSLog(@"%ld",countOfObjec);
通過(guò)快速枚舉來(lái)遍歷數(shù)組元素
NSArray *testArray = @[@1,@2,@3,@4,@5];
for (id object in testArray) {
NSLog(@"%@",object);
}
for (NSNumber *object in testArray) {
NSLog(@"%@",object);
}
快速遍歷集合
for (id object in set1) {
NSLog(@"%@",object);
}
快速遍歷字典
直接遍歷字典直接得到的是字典的每一個(gè)鍵，可以通過(guò)遍歷得到的鍵去獲取對(duì)應(yīng)的值
for (NSString *key in dic1) {
NSLog(@"dictionary[%@]:%@",key,dic1[key]);
}
//??? dic1[key]就相當(dāng)于[dic1 objectForKey:key]
文章轉(zhuǎn)載自
