Objective-C之Foundation框架中的NSDictionary的用法以及它的遍历方法

常用与创建NSDictionary的方法：

+ (id)dictionary;

+ (id)dictionaryWithObjtct:(id)object forKey:(id <NSCopying>)key;

+ (id)dictionaryWithObjectAndKeys:(id)firstObject,...

+ (id)dictionaryWithDictionary:(NSDictionary *)dict

+ (id)dictionaryWithObjects:(NSArray *)objects forKeys:(NSArray *)keys

- (id)initWithObjectsAndKeys:(id)firstObject,...

- (id)initWithDictionary:(NSDictionary *)otherDictionary

- (id)initWithObjects:(NSArray *)objects forKeys:(NSArray *)keys

+ (id)dictionaryWithConentsOfFile:(NSString *)url

+ (id)dictionaryWithCOntentsURL:(NSString *)path

- (id)initWithContentsOfFile:(NSString *)path

- (id)initWithContentsOfURL:(NSString *)url

常用方法：

//多少键值对

- (NSUInteger)count;

//比较两个字典

- (Bool)isEqualToDictionary:(NSDictionary *)otherDictionary

//将一个NSDictionary持久化到一个文件中

- (Bool)writeToFile:(NSString *)path atomically:(Bool)useAuxiliaryFile

//返回所有的key

- (NSArray *)allKeys

//返回Object元素对应的所有key

- (NSArray *)allKeysForObject:(id)anObject

//返回所有的value

- (NsArray *)allValues

//根据key返回value

- (id)objectForKey:(id)akey

//返回keys对应的所有value，如果没有对应的value，用marker代替，根据多个key返回多个value

//当可以找不到对应的value时，用marker代替

- (NSArray *)objectsForKeys:(NSArray *)keys notFoundMarker:(id)marker

字典的遍历：

1、快速遍历：

for (NSString *key in dict)

2、迭代器遍历：

//key迭代器

- (NSEnumerator *)keyEnumerator

//对象迭代器

- (NSEnumerator *)objectEnumerator

3、block遍历：见下面测试demo代码

4、字典的内存管理：

见下面测试demo代码

对key排序(用法和NSArray排序类似)：

- (NSArray *)keysSortedByValueUsingComparator:(NSComparator)cmptr

- (NSArray *)kyesSortedByValueWithOptions:(NSSortOptions)opts  usingComparator:(NSComparator)cmptr

- (NSArray *)keysSortedByValueUsingSelector:(SEL)comparator

测试demo如下：

void dictCreate(){

   

    NSDictionary *dict = [NSDictionary dictionaryWithObject:@"test" forKey:@"t"];

    NSLog(@"%@", dict);

}

void dictUse(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:

                          @"a",@"k1",

                          @"b",@"k2",

                          @"c",@"k3",

                          nil];

   

    NSLog(@"count=%zi", dict.count);

    //write to file

    NSString *path = @"/Users/gongpb/develop/NSDictionary/NSDictionary/dict.xml";

    [dict writeToFile:path atomically:YES];

   

    dict = [NSDictionary dictionaryWithContentsOfFile:path];

    NSLog(@"dict:%@",dict);

   

    NSArray *array = [dict objectsForKeys:[NSArray arrayWithObjects:@"k1",@"k4", nil]  notFoundMarker:@"not found"];

    NSLog(@"find result:%@",array);

 }

//快速遍历

void dictFor1(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:

                          @"a",@"k1",

                          @"b",@"k2",

                          @"c",@"k3",

                          nil];

    for (id key in dict) {

        id value=[dict objectForKey:key];

        NSLog(@"%@=%@",key,value);

    }

}

//迭代器遍历

void dictFor2(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:

                          @"a",@"k1",

                          @"b",@"k2",

                          @"c",@"k3",

                          nil];

  

    NSEnumerator *enumer = [dict keyEnumerator];

    id key = nil;

    while (key = [enumer nextObject]) {

        id value = [dict objectForKey:key];

        NSLog(@"%@=%@",key,value);

    }

}

#pragma mark block遍历

void dictFor3(){

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:

                          @"a",@"k1",

                          @"b",@"k2",

                          @"c",@"k3",

                          nil];

   [dict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {

       NSLog(@"%@=%@",key,obj);

   }];

  

}

//字典内存管理

void dictMemory(){

    Student *stu1 = [Student studentWithName:@"stu1"];

    Student *stu2 = [Student studentWithName:@"stu1"];

    Student *stu3 = [Student studentWithName:@"stu1"];

    //一个对象作为字典的key或者value时，会做一次retain操作，计数器会加一

    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:

                          stu1,@"k1",

                          stu2,@"k2",

                          stu3,@"k3",

                          nil];

   // 当字典被销毁时，里面所有key和value都会有一次releas操作，计数器减一

    NSLog(@"%@",dict);

   

   

}

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

{

    @autoreleasepool {

      

        NSLog(@"-------dictCreate------");

       // dictCreate();

        NSLog(@"-------dictUse----------");

        dictUse();

        NSLog(@"-------dictFor1---------");

        dictFor1();

        NSLog(@"-------dictFor2----------");

        dictFor2();

        NSLog(@"-------dictFor3-----------");

        dictFor3();

        NSLog(@"-------dictMemory---------");

        dictMemory();

    }

    return 0;

}

.h文件：

#import <Foundation/Foundation.h>

@interface Student : NSObject

@property (nonatomic,retain)NSString *name;

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

@end

.m文件：

#import "Student.h"

@implementation Student

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

    Student *stu = [[[Student alloc] init] autorelease];

    stu.name = name;

    return stu;

}

- (void)dealloc{

    NSLog(@"student:%@  is destroyed",_name);

    [super dealloc];

}

@end