黑马程序员-Object C之NSDirectory和NSMutableDirectory的基本使用

来源：互联网发布：论大数据的机遇和挑战编辑：程序博客网时间：2024/06/16 03:29

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NSDictionary 不可变的字典

例子代码解析：

#pragma mark 字典的初始化void dictCreate() {    // NSDictionary是不可变的    NSDictionary *dict = [NSDictionary dictionaryWithObject:@"v" forKey:@"k"];        // 最常用的初始化方式，结尾必须使用nil标志结束    dict = [NSDictionary dictionaryWithObjectsAndKeys:            @"v1", @"k1",            @"v2", @"k2",            @"v3", @"k3", nil];        NSArray *objects = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];    NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];    dict = [NSDictionary dictionaryWithObjects:objects forKeys:keys];//使用NSArray的值初始化字典    NSLog(@"%@", dict);}#pragma mark 字典的基本用法void dictUse() {    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:            @"v1", @"k1",            @"v2", @"k2",            @"v3", @"k3", nil];        // count是计算有多少个键值对(key-value)    NSLog(@"count=%zi", dict.count);        // 由于NSDictionary是不可变的，所以只能取值，而不能修改值    id obj = [dict objectForKey:@"k2"];    NSLog(@"obj=%@", obj);        // 将字典写入文件中    NSString *path = @"/Users/wenli/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);        NSArray *objects = [dict allValues];    //NSLog(@"objects=%@", objects);        // 根据多个key取出对应的多个value    // 当key找不到对应的value时，用marker参数值代替    objects = [dict objectsForKeys:[NSArray arrayWithObjects:@"k1", @"k2", @"k4", nil] notFoundMarker:@"not-found"];    NSLog(@"objects=%@", objects);}#pragma mark 遍历字典void dictFor() {    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:                          @"v1", @"k1",                          @"v2", @"k2",                          @"v3", @"k3", nil];    // 遍历字典的所有key    for (id key in dict) {        id value = [dict objectForKey:key];        NSLog(@"%@=%@", key, value);    }}#pragma mark 遍历字典2void dictFor2() {    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:                          @"v1", @"k1",                          @"v2", @"k2",                          @"v3", @"k3", nil];    // key迭代器    NSEnumerator *enumer = [dict keyEnumerator];    id key = nil;    while ( key = [enumer nextObject]) {        id value = [dict objectForKey:key];        NSLog(@"%@=%@", key, value);    }        // 对象迭代器    // [dict objectEnumerator];}#pragma mark 遍历字典3void dictFor3() {    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:                          @"v1", @"k1",                          @"v2", @"k2",                          @"v3", @"k3", nil];    [dict enumerateKeysAndObjectsUsingBlock://该方法<span style="color: rgb(51, 51, 51); font-family: 宋体;font-size:10px; line-height: 21px;">会遍历dictionary并把里面所有的key和value一组一组的展示</span>     ^(id key, id obj, BOOL *stop) {        NSLog(@"%@=%@", key, obj);    }];}#pragma mark void dictMemory() {    Student *stu1 = [Student studentWithName:@"stu1"];    Student *stu2 = [Student studentWithName:@"stu2"];    Student *stu3 = [Student studentWithName:@"stu3"];        // 一个对象称为字典的key或者value时，会做一次retain操作，也就是计数器会+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}

NSMutableDirectory 不可变的字典

例子代码演示：

    // 创建一个空的字典    NSMutableDictionary *dict = [NSMutableDictionary dictionary];    Student *stu1 = [Student studentWithName:@"stu1"];        // 添加元素    // stu1的计数器会+1    [dict setObject:stu1 forKey:@"k1"];    NSLog(@"stu1:%zi", [stu1 retainCount]);        // 添加其他字典other到当前字典dict中    NSDictionary *other = [NSDictionary dictionaryWithObject:@"v2" forKey:@"k2"];    [dict addEntriesFromDictionary:other];        // 删除所有的键值对    // [dict removeAllObjects];        // 删除k1对应的元素stu1，stu1会做一次release操作    [dict removeObjectForKey:@"k1"];    NSLog(@"stu1:%zi", [stu1 retainCount]);        // 删除多个key对应的value    // [dict removeObjectsForKeys:[NSArray arrayWithObject:@"k1"]];    // 字典被销毁时，内部的所有key和value计数器都会-1，也就是说stu1会release一次

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