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须读:看完该文章你能做什么？

NSDictionary的基本使用

学习前:你必须会什么?（在这里我已经默认你具备C语言的基础了）

适合所有人，不需要懂的什么

注:(小白直接上手)

一、本章笔记

 key(标识) 为了方便查找那个值
 一、字典
    1.如何创建
    + (instancetype)dictionaryWithObject:(ObjectType)object forKey:(KeyType <NSCopying>)key;
    + (instancetype)dictionaryWithObjects:(NSArray<ObjectType> *)objects forKeys:  (NSArray<KeyType <NSCopying>> *)keys;
    获取
    - (nullable ObjectType)objectForKey:(KeyType)aKey;

    2.字典的三种遍历方式
        2.1 for
        2.2 for in
        2.3 block
         - (void)enumerateKeysAndObjectsUsingBlock:(void (NS_NOESCAPE ^)(KeyType key, ObjectType obj, BOOL *stop))block NS_AVAILABLE(10_6, 4_0);
    3.字典的文件读写
        - (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile;
        + (nullable NSDictionary<KeyType, ObjectType> *)dictionaryWithContentsOfFile:(NSString *)path;

二、code

main.m

#pragma mark 08-NSDictionary

#pragma mark - 代码
#import <Foundation/Foundation.h>
#pragma mark 类

#pragma mark - main函数
int main(int argc, const char * argv[])
{
#pragma 1.如何创建
    NSDictionary *dict = [NSDictionary dictionaryWithObject:@"lyh" forKey:@"name"];
    NSString *name = [dict objectForKey:@"name"];
    NSLog(@"name = %@",name);
    
    // 注意 : key 和 value 是一一对应的
    NSDictionary *dict2 = [NSDictionary dictionaryWithObjects:@[@"lyh",@"25"] forKeys:@[@"name",@"age"]];
    NSLog(@"%@ %@",[dict2 objectForKey:@"name"],[dict2 objectForKey:@"age"]);
#pragma 创建、获取的快捷方式
//    NSDictionary *dict3 = @{key:value};
    NSDictionary *dict3 = @{@"name":@"lyh"};
    NSLog(@"name = %@",dict3[@"name"]);

    NSDictionary *dict4 = @{@"name":@"lyh",@"age":@"25",@"height":@"171.1"};
    NSLog(@"name = %@ , age = %@",dict4[@"name"],dict4[@"age"]);

#pragma 2.字典的遍历
    // 方式1 for
    /*
    // 2.1 如何获取字典中 的 key 和 value的个数,在字典中 key称之为键, value称之为值
    NSLog(@"count = %lu",[dict4 count]);
    
    for (int i = 0 ; i < dict4.count; ++i) {
        // 获取字典中所有的key
        NSArray *keys  = [dict4 allKeys];
        // 期初当前位置对应的key
//        NSLog(@"%@",keys[i]);
        NSString *key = keys[i];
        NSString *value = dict4[key];
        NSLog(@"key = %@, value = %@",key,value);
    }
     */
    
    // 方式2 for in
    /*
    // 如果通过forin 遍历 ,会将所有的key赋值给前面的obj
    for (NSString *key in dict4) {
        NSLog(@"%@",key);
        NSString *value = dict4[key];
        NSLog(@"key = %@, value = %@",key,value);
    }
     */
    // 方式3 迭代器
    [dict4 enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
        NSLog(@"key = %@, value = %@",key,obj);
    }];
#pragma 3.字典的文件读写
    // 写
    [dict4 writeToFile:@"/Users/liyuhong165/Desktop/temp/day08/abcd.plist" atomically:YES];
    
    // 读
    
    // 注意 : 字典 和 数组不同, 字典中保存的数据是无序的
    NSDictionary *newDict = [NSDictionary dictionaryWithContentsOfFile:@"/Users/liyuhong165/Desktop/temp/day08/abcd.plist"];
    NSLog(@"newDict = %@",newDict);
    return 0;
}

Person

>>>.h
>>>.m