Foundation框架(9)——NSDictionary的初始化、用法、遍历、内存管理

//
//  main.m
//  Foundation框架(9)
//
//  Created by XinYou on 15-1-21.
//  Copyright (c) 2015年 vxinyou. All rights reserved.
//

#import 
#import "Student.h"

#pragma mark 字典的初始化
void dictCreate(){
    // 第一种初始化方式，NSDictionary是不可变的
    NSDictionary *dict = [NSDictionary dictionaryWithObject:@"v1" forKey:@"k1"];
    // 最常用的初始化方式
    dict = [NSDictionary dictionaryWithObjectsAndKeys:
            @"v1", @"k1",
            @"v2", @"k2",
            @"v3", @"k3", nil];
    
    NSArray *values = [NSArray arrayWithObjects:@"v7", @"v8", @"v9", nil];
    NSArray *keys = [NSArray arrayWithObjects:@"k7", @"k8", @"k9", nil];
    // 第三种初始化方式
    dict = [NSDictionary dictionaryWithObjects:values forKeys:keys];
    
    NSLog(@"dict = %@", dict);
}

#pragma mark 字典的基本用法
void dictUse(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    // count是计算有多少键值对
    NSLog(@"count = %zi", [dict count]);// count = 3
    // 取出某个键对应的值
    id obj = [dict objectForKey:@"k2"];
    NSLog(@"obj = %@", obj);// obj = v2
    
    // 将字典写入文件中
    NSString *path = @"/Users/xinyou/Desktop/dict.xml";
    [dict writeToFile:path atomically:YES];

    // 从文件中读取内容
    dict = [NSDictionary dictionaryWithContentsOfFile:path];
    NSLog(@"dict = %@", dict);
}

#pragma mark 字典的其他用法
void dictUse2(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    // 返回所有的key
    NSArray *keys = [dict allKeys];
    NSLog(@"keys = %@", keys);
    
    // 返回所有的value
    NSArray *values = [dict allValues];
    NSLog(@"values = %@", values);
    
    // 根据多个key取出对应的多个value
    // 当key找不到对应的value时，取默认值"noValue"
    values = [dict objectsForKeys:[NSArray arrayWithObjects:@"k1", @"k2", @"k6", nil] notFoundMarker:@"noValue"];
    
    NSLog(@"values = %@", values);
}


#pragma mark 遍历字典
void dictFor(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    
    // 注意：这里遍历的是字典的所有key，而不是键值对
    for(id key in dict){
    
        id value = [dict objectForKey:key];
        NSLog(@"%@ = %@", key, value);
    
    }

}


#pragma mark 遍历字典2
void dictFor2(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    
    // 获取key迭代器
    NSEnumerator *enume = [dict keyEnumerator];
    id key = nil;
    while (key = [enume nextObject]) {
        id value = [dict objectForKey:key];
        NSLog(@"%@ = %@", key, value);
    }
    
    // 获取value迭代器
    // [dict objectEnumerator];
}


#pragma mark 遍历字典3
void dictFor3(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"v1", @"k1",
                          @"v2", @"k2",
                          @"v3", @"k3", nil];
    // 使用block对字典进行遍历
    [dict enumerateKeysAndObjectsUsingBlock:
     ^(id key, id obj, BOOL *stop) {
         NSLog(@"%@ = %@", key, obj);
    }];

}

#pragma mark 字典的内存管理
void dictMemory(){

    Student *stu1 = [Student studentWithName:@"zhangsan"];
    Student *stu2 = [Student studentWithName:@"lisi"];
    Student *stu3 = [Student studentWithName:@"wangwu"];
    
    // 一个对象成为字典的key或者value时，会做一次retain操作，也就是这个对象的计数器会+1
    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                          stu1, @"k1",
                          stu2, @"k2",
                          stu3, @"k3", nil];
    // 当字典被销毁时，里面的所有key和value都会做一次release操作，也就是计数器会-1
}

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

    @autoreleasepool {
        
//        dictCreate();
//        dictUse();
//        dictUse2();
//        dictFor();
//        dictFor2();
//        dictFor3();
        dictMemory();
    }
    return 0;
}

//
//  Student.h
//  Foundation框架(9)
//
//  Created by XinYou on 15-1-21.
//  Copyright (c) 2015年 vxinyou. All rights reserved.
//

#import 

@interface Student : NSObject

@property (nonatomic, retain) NSString *name;

+ (id)studentWithName:(NSString *)name;

@end
//
//  Student.m
//  Foundation框架(9)
//
//  Created by XinYou on 15-1-21.
//  Copyright (c) 2015年 vxinyou. All rights reserved.
//

#import "Student.h"

@implementation Student


+ (id)studentWithName:(NSString *)name{

    Student *stu = [[[Student alloc] init] autorelease];
    
    stu.name = name;
    
    return stu;
    
}

- (void)dealloc{
    
    NSLog(@"%@被销毁了", _name);
    
    [_name release];

    [super dealloc];
}

@end