【黑马程序员】OC-Foundation框架—NSDictionary和NSMutableDictionary

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一、NSDictionary介绍

1)什么是NSDictionary

NSDictionary翻译过来叫做”字典”

日常生活中, “字典”的作用: 通过一个拼音或者汉字, 就能找到对应的详细解释

NSDictionary的作用类似: 通过一个key(键), 就能找到对应的value(值) NSDictionary是不可变的, 一旦初始化完毕, 里面的内容就无法修改

<span style="font-size:14px;">//
//  main.m
//  NSDictionary介绍
//
//  Created by Brisinga on 15/11/18.
//  Copyright © 2015年 itcast. All rights reserved.
//

#import <Foundation/Foundation.h>

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

//创建空字典
NSDictionary *d1 = [NSDictionary dictionary];
//创建只有一组键值对的字典
NSDictionary *d2 = [NSDictionary dictionaryWithObject:@"zhangsanfeng" forKey:@"jsf"];
//创建多组键值对的字典
NSDictionary *d3 = [NSDictionary dictionaryWithObjectsAndKeys:@"hufei",@"hf",@"leifeng",@"lf", nil];
//打印字典
NSLog(@"%@",d3);

//快速创建一个字典
NSDictionary *d4 = @{@"zs":@"zhangsan",@"ls":@"lisi"};
NSLog(@"%@",d4);

//打印字典长度
NSLog(@"%ld",d4.count);

//根据key值取出value值
NSLog(@"%@",[d4 objectForKey:@"ls"]);
NSLog(@"%@",d4[@"zs"]);

//字典的遍历
//方法一  //获取的是对应的key
for (NSString *str in d4) {
NSLog(@"%@",d4[str]);
}
//方法二
[d4 enumerateKeysAndObjectsUsingBlock:^(id   key, id   obj, BOOL * _Nonnull stop) {
NSLog(@"%@ = %@",key,obj);
}];

}
return 0;
}
</span>

二、NSDictionary的简写以及文件操作

<span style="font-size:14px;">//
//  main.m
//  NSDictionary的简写以及文件操作
//
//  Created by Brisinga on 15/11/18.
//  Copyright © 2015年 itcast. All rights reserved.
//

#import <Foundation/Foundation.h>

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

//简写创建dictionary
NSDictionary *d = @{@"zbz":@"zhangbozhi",@"cgx":@"chenguanxi",@"hl":@"hello"};

//简写形式获取key对应的value
NSString *str = d[@"zbz"];
NSLog(@"%@",str);

//把字典保存到文件中
[d writeToFile:@"/Users/Brisinga/Desktop/a.plist" atomically:YES];

//从文件中读取字典
NSDictionary *d2 = [NSDictionary dictionaryWithContentsOfFile:@"/Users/Brisinga/Desktop/a.plist"];
NSLog(@"%@",d2);

//应用：
//省市
//辽宁   大连
//       沈阳
//河北    保定
//       石家庄

NSArray *arr1 = @[@"dalian",@"shenyang"];
NSArray *arr2 = @[@"baoding",@"shijiazhuang"];
NSDictionary *d3 = @{@"ln":arr1,@"hb":arr2};
[d3 writeToFile:@"/Users/Brisinga/Desktop/a.plist" atomically:YES];
//打印字典
for (NSString *key in d3) {
NSLog(@"%@",d3[key]);
}
//方法二
[d3 enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
for (NSString *str in obj) {
NSLog(@"%@:%@",key,str);
}
}];
//获取每一个数组
arr1 = d3[@"ln"];
NSLog(@"%@",arr1);
}
return 0;
}
</span>

三、NSMutableDictionary的介绍和使用

<span style="font-size:14px;">//
//  main.m
//  NSMutableDictionary的介绍和使用
//
//  Created by Brisinga on 15/11/18.
//  Copyright © 2015年 itcast. All rights reserved.
//

#import <Foundation/Foundation.h>

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

//1）可变字典的创建
NSMutableDictionary *d1 = [NSMutableDictionary dictionary];
NSMutableDictionary *d2 = [NSMutableDictionary dictionaryWithCapacity:5];

//2）可变字典添加键值对
[d1 setObject:@"zhangbozhi" forKey:@"zbz"];
[d1 setValue:@"liuneng" forKey:@"ln"];
NSLog(@"%@",d1);
//3）删除
[d1 removeObjectForKey:@"zbz"];
//4）修改
[d1 setValue:@"zhang" forKey:@"zbz"];
[d1 setObject:@"liaoning" forKey:@"ln"];
d1[@"ln"] = @"llllnnn";
NSLog(@"%@",d1);
//5）查找
NSArray *arr = [d1 allKeys];  //获取所有key
if([arr containsObject:@"ln"]){
NSLog(@"存在");
}
}
return 0;
}</span>