Snail—OC学习之字典NSDictionary

NSDictionary 是根据键值对来存储数据的 是无序、不可重复的

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

@autoreleasepool {

//--------------------对象的方法-----------------------//
//初始化一个字典
NSDictionary * dict1 = [[NSDictionary alloc] init];
//根据一个字典初始化一个新的字典
NSDictionary * dict2 = [[NSDictionary alloc] initWithDictionary:dict1];
//初始化一个字典 并添加一个键(数组 多个元素) 值(数组 多个元素)
NSArray * keys = @[@"1",@"2",@"3"];
NSArray * values = @[@"one",@"two",@"three"];
NSDictionary * dict3 = [[NSDictionary alloc] initWithObjects:values forKeys:keys];
NSLog(@"%@",dict3);
//初始化一个字典 手动添加键值对 值,键,值,键,nil
NSDictionary * dict4 = [[NSDictionary alloc] initWithObjectsAndKeys:@"one",@"1",@"two",@"2",nil];
NSLog(@"%@",dict4);
//xcode4.6后简易写法 键:值,键:值
NSDictionary * dict5 = @{@"key1":@"value1",@"key2":@"value2"};

//--------------------类方法创建对象-----------------------//
[NSDictionary dictionary];
[NSDictionary dictionaryWithDictionary:dict2];
[NSDictionary dictionaryWithObjectsAndKeys:@"one",@"1", nil];
[NSDictionary dictionaryWithObjects:values forKeys:keys];

//--------------------常用方法-----------------------//
//通过键 找到对应的值
NSString * string = [dict4 objectForKey:@"1"];
//得到键值对的对数
NSInteger count = [dict4 count];
//取得多有键 返回值为数组
NSArray * allKeys = [dict4 allKeys];
//取得所有值 返回值为数组
NSArray * allValues = [dict4 allValues];
//xcode4.6后 通过键找到对应值的简易写法
NSString * string1 = dict4[@"2"];
NSLog(@"%@",string1);

}
return 0;
}