objective-c系列-NSDictionary&NSMutableDictionary

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NSDictionary

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// 字典的概念：

// 键值对的概念:

// 查字典时：用一个键，得到一个值

字典的构造方法:

NSDictionary * dict1 = [[NSDictionary alloc]initWithObjectsAndKeys:@"one",@"1",@"two",@"2",@"three",@"3", nil];

NSLog(@"dict1: %@", dict1);

// 字典的字面常量对象:

// 1, 1,3, "abc", @"abc", @[@"abc",@""] @{@"key":@"value",@"k2":@"v2"}

// NSDictionary * dict2 = @{@"1":@"one",@"2":@"two",@"3":@"three"};

#define DICT @{@"1":@"one",@"2":@"two",@"3":@"three"}

NSDictionary * dict2 = DICT;//DICT是一个宏

NSLog(@"dict2: %@",dict2);

NSDictionary * dict3 = [[ NSDictionary alloc]initWithDictionary:dict2];

NSLog(@"dict3: %@", dict3);

NSArray * keys =@[@"key1",@"key2",@"key3"];

NSArray * values =@[@"value1",@"value2",@"value3"];

NSDictionary * dict4 = [[ NSDictionary alloc]initWithObjects:values forKeys:keys];

NSLog(@"dict4: %@", dict4);

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//根据键查值

NSDictionary * dict1 = @{@"1":@"one",@"2":@"two",@"3":@"three"};

NSString * key = @"1";

// 根据一个键，得到一个值,如果字典中没有这个键值对，则objectForKey:这个方法返回一个nil

NSString *value = [dict1 objectForKey:key];

NSString *value2 = dict1[key];

NSString *value3 = dict1[@"2"];

//从终端获取一个key,得到一个值

char buf[128];

// fgets 和 gets的区别:

// gets:从终端的输入缓冲区不断地获取字符存入buf，直到遇到回车符结束，

// 但是最后的那个回车符不会存入buf,只会往buf后边补一个'\0'

// -> abc\n buf: abc\0

// fgets(buf, 122, stdin): 从终端的输入缓冲区不断地获取字符，但最多只能获取122个字符,如果不够122个字符时就遇到了回车符，那么回车符也

// 会放入buf, 且在回车符后边再补一个'\0'

// -> abc\n buf: abc\n\0

while (1) {

NSLog(@"请输入一个key：");

#if 0

fgets(buf, 122, stdin);

buf[strlen(buf)-1]='\0';

#else

gets(buf);

#endif

NSString *inputKey = [NSString stringWithUTF8String:buf];

NSString * getValue = [dict1 objectForKey:inputKey];

NSLog(@"值为: %@", getValue);

}

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//遍历字典

NSDictionary * dict1 = @{@"33":@"three",@"1":@"one",@"2":@"two",@"3":@"three"};

// 获取字典所有的键

NSArray *keys=[dict1 allKeys];

// 获取字典所有的值

NSArray *values = [dict1 allValues];

id key;

//快速遍历字典的所有键

for(key in dict1)

{

NSLog(@"key: %@",key);

NSLog(@"value: %@", dict1[key]);

}

//注意: 从字典获取的枚举器枚举的是字典的所有值，而不是键

NSEnumerator *enumerator = [dict1 objectEnumerator];

id obj;

while (obj=[enumerator nextObject])

{

NSLog(@"obj: %@", obj);

//注意:词典中:值可以相同，但键不能相同,即一个值可以有多个键

NSArray * keysOfObj= [dict1 allKeysForObject:obj];

NSLog(@"某个值对应的所有键为:%@",keysOfObj);

}

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// 其他方法：

//1, 获取字典的键值对数量

NSDictionary * dict1 = DICT;

NSUInteger count = [dict1 count];

NSLog(@"字典一共有%lu个键值对", count);

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NSMutableDictionary

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可变字典的构造方法：

//构造一个空字典

NSMutableDictionary *mdict = [NSMutableDictionary dictionary];

NSMutableDictionary *mdict1=[[NSMutableDictionary alloc]init];

NSMutableDictionary * mdict2 = [[NSMutableDictionary alloc]initWithObjectsAndKeys:@"v1",@"k1",@"v2",@"k2", nil];

NSMutableDictionary * mdict3 = [[ NSMutableDictionary alloc]initWithObjects:@[@"vx1",@"vx2",@"vx3"] forKeys:@[@"kx1",@"kx2",@"kx3"]];

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添加键值对：

NSMutableDictionary *mdict1=[[NSMutableDictionary alloc]init];

[mdict1 setObject:@"setV1" forKey:@"setK1"];

[mdict1 setObject:@"setV1" forKey:@"setK2"];

NSLog(@"mdict1: %@", mdict1);

NSLog(@"两个值的地址分别为:%p %p", mdict1[@"setK1"], mdict1[@"setK2"]);

NSLog(@"两个abc的地址分别为: %p %p", @"abc", @"abc");

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修改键值对：

NSMutableDictionary * mdict1 = [[NSMutableDictionary alloc]initWithObjectsAndKeys:@"v1",@"k1",@"v2",@"k2", nil];

//现在时刻，mdict1 : k1=v1 k2=v2

// 修改某一个键对应的值, 让键 k2的值不再是 v2

[mdict1 setObject:@"this is newValue for k2" forKey:@"k2"];

NSLog(@"mdict1: %@", mdict1);

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删除键值对：

NSMutableDictionary * mdict2 = [[NSMutableDictionary alloc]initWithObjectsAndKeys:@"v1",@"k1",@"v2",@"k2",@"v3",@"k3", @"v5",@"k5",@"v6",@"k6",nil];

NSLog(@"原始字典: mdict2: %@", mdict2);

//删除一个键值对，需要传入一个键

[mdict2 removeObjectForKey:@"k2"];

NSLog(@"删除一个键对应的键值对后:mdict2: %@", mdict2);

//删除一组键对应的键值对，传入一个键的数组

[mdict2 removeObjectsForKeys:@[@"k5",@"k6"]];

NSLog(@"删除一组键对应的键值对后:mdict2: %@", mdict2);

//重置字典，即原来的所有键值对无效了。

[mdict2 setDictionary:@{@"newKey1":@"newValue1",@"newKey2":@"newValue2"}];

//删除所有键值对

[mdict2 removeAllObjects];

NSLog(@"删除所有键值对后:mdict2: %@", mdict2);

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巴特西

objective-c系列-NSDictionary&NSMutableDictionary

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