NSDictionary（字典）
一、创建字典的方式
1.创建空的字典
NSDictionary *dic1=[[NSDictionary alloc]init];
NSDictionary *dic2=[NSDictionary dictionary];
NSLog(@"%@,%@",dic1,dic2);
2.创建有内容的字典
NSDictionary *dictionary1=[NSDictionary dictionaryWithObject:@"Value"forKey:@"key"];
NSLog(@"%@",dictionary1);
NSDictionary *dictionary2=[[NSDictionary alloc]initWithObjects:@[@"V1",@"V2",@"V3"]forKeys:@[@"K1",@"K2",@"K3"]];
NSDictionary *dictionary3=[NSDictionary dictionaryWithObjectsAndKeys:@"V1",@"K1",@"V2",@"K2",nil];
NSLog(@"%@",dictionary2);
示例：自己封装一个学生信息的字典
NSString *stu_name=@"Tom";
NSArray *stu_score=@[@90,@100,@80];
NSArray *valueArray=@[@20,stu_name,stu_score];
NSDictionary *stuDic=[NSDictionary dictionaryWithObjects:valueArray forKeys:@[@"age",@"name",@"score"]];
NSLog(@"%@",stuDic);
3.根据已有字典创建新的字典
NSDictionary *dictionary4=[NSDictionary dictionaryWithDictionary:dictionary3];
4.获取字典中所有元素（键值对）的个数
NSLog(@"dictionary4.count: %ld",[dictionary4 count]);
5.根据Key获取value值
NSString *value1=[dictionary4 valueForKey:@"K1"];
NSLog(@"value1=%@",value1);
NSArray *value_array=[stuDic valueForKey:@"score"];
NSLog(@"%@",value_array);
6.获取字典中所有的Key和value
NSArray *keyArray=[dictionary4 allKeys];
NSArray *value_Array=[dictionary4 allValues];
NSLog(@"%@,%@",keyArray,value_Array);
NSMutableDictionary (可变字典)
1.创建可变字典（注意：可变字典必须进行开辟空间操作！）
NSMutableDictionary *mutabledic1=[NSMutableDictionary dictionaryWithObjects:@[@"v1",@"v2",@"v3"]forKeys:@[@"k1",@"k2",@"k3"]];
NSLog(@"%@",mutabledic1);
2.添加元素（键值对）
[mutabledic1 setObject:@"v4"forKey:@"k4"];//可以是k3，直接覆盖，所以是set
NSLog(@"%@",mutabledic1);
3.根据已经存在的字典添加
[mutabledic1 addEntriesFromDictionary:dictionary4];
NSLog(@"%@",mutabledic1);
4.修改（update）：
//将当前字典中所有元素替换成新的字典元素
NSDictionary *dic3=[NSDictionary dictionaryWithObjects:@[@"A",@"B",@"C"]forKeys:@[@"A1",@"A2",@"A3"]];
[mutabledic1 setDictionary:dic3];
NSLog(@"%@",mutabledic1);
//指定Key值修改
[mutabledic1 setObject:@"NewA"forKey:@"A1"];
NSLog(@"%@",mutabledic1);
//删除
[mutabledic1 removeObjectForKey:@"A2"];//指定Key删除
[mutabledic1 removeObjectsForKeys:@[@"A1",@"A2"]];//指定多个Key删除
[mutabledic1 removeAllObjects];//删除所有
}
//给数组进行排序的方法
NSArray *keyArray =[[alldictionary allKeys]sortedArrayUsingSelector:@selector(compare:)];
