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//通过唯一的key找到对应的value（键 值）
//不可变
//通过索引找到内容
//也是只能放OC对象，不能放基本数据类型和空值
#pragma mark create dictionary
void dictCreate(){
//most commom used +
NSdictionary *dict=[NSDictionary dictionaryWithObject:@”v” forKey:@”key”];
//+method can’t change
dict=[NSDictionary dictoryWithObjectsAndKeys:
@”v1”,@”k1”,
@”v2”,@”k2”,
@”v3”,@”k3”,
@”v4”,@”k4”,
,nil];
NSArray *objects=[NSArray arrayWithObjects:@”v1”,@”v2”,@”v3”,nil];
NSArray *keys=[NSArray arrayWithObjects:@”k1”,@”k2”,@”k3”,nil];
dict=[NSDictionary dictoryWithObjects:objects forKeys:keys];
NSLog(@“%@”，dict); //array->() dict->{}
}
#pragma mark dict use
void dictUse(){
NSDictionary *dict=[NSDictionary dictoryWithObjectsAndKeys:
@”v1”,@”k1”,
@”v2”,@”k2”,
@”v3”,@”k3”,
@”v4”,@”k4”,
,nil];
NSDictionary NSLog(@”count=%zi”,[dict count]); //dict.count how many couples
//通过key找value
NSLog(@”k2-> %@”,[dict objectForKey:@”k2”]);//只能取值不能改值
//can write a dictionary to a file
NSString *path =@”/User/apple/Desktop/dict.xml”;
[dict writeToFile:path atomically:YES];
//从文件中读取字典对象（按照格式才能）
NSDictionary dict2=[NSDictionary dictonaryWithContentOfFile:path];
}
#pragma mark use2
void dictUse2(){
dict=[NSDictionary dictoryWithObjectsAndKeys:
@”v1”,@”k1”,
@”v2”,@”k2”,
@”v3”,@”k3”,
@”v1”,@”k4”,
,nil];
NSLog(@”dict all keys is”,[dict allKeys]);//他是无序的，需要的话NSArray去排序
//key是唯一 value不一定 不能一对多 可以多对一
//当一对多时返回所有的value
//all values
NSArray *array1=[dict allKeysForObject:@”v1”];
NSArray *objects=[dict allValues];
//根据多个key取出多个value
id objects=[dict objectForKeys:[NSArray arrayWithObjects:@”k1”,@”k2”,@”k4”,nil] notFoundMarker:@“not-found”]; //v1 v2
//notFoundMarker 如果找不到对应的值的时候就用marker来替代
}
#pragma mark traverse dictionary
void dictTraverse(){
dict=[NSDictionary dictoryWithObjectsAndKeys:
@”v1”,@”k1”,
@”v2”,@”k2”,
@”v3”,@”k3”,
@”v1”,@”k4”,
,nil];
//1
for(id key in dict)//因为key是唯一{
id value=[dict objectForKey:key];
NSLog(@”%@=%@”,key,value);
}
}
#pragma mark traverse dic with enumerator
void dictTraverseDict(){
//2迭代器 key
dict=[NSDictionary dictoryWithObjectsAndKeys:
@”v1”,@”k1”,
@”v2”,@”k2”,
@”v3”,@”k3”,
@”v1”,@”k4”,
,nil];
NSEnumerator *enumer=[dict keyEnumerator];
id key=nil;
while(key=[enumer nextObject]){
id value=[dict objectForKey:key];
NSLog(@”%@=%@”,key,value);
}
//对象迭代器 value
NSEnumerator *enumer=[dict objectEnumerator];
}
#pragma mark traverse dic with block
void dictTraverseDict(){
dict=[NSDictionary dictoryWithObjectsAndKeys:
@”v1”,@”k1”,
@”v2”,@”k2”,
@”v3”,@”k3”,
@”v1”,@”k4”,
,nil];
[dict enumerateKeysAndObjectsUsngBlock:^(id key,id obj,BOOL stop){
NSLog(@”%@=%@”,key,obj);
}];
}
#pragma mark sort key
#pragma mark memory management
Student.h
@property (nonatomic,retain)NSString * name;
+(id)studentWithName:(NSString *)name;
Student.m
+(id)studentWithName:(NSString *)name{
Student *stu=[[Student alloc]init];
stu.name=name;
return [stu autorelease];
}
-(void)dealloc{
NSLog(@”%@ is destroied”,self.name);//_name
[super dealloc];
}
main.m
#import “Student.h”
//不管是key 还是value 都会对对象进行retain操作
void dicMemory(){
Student *stu1=[Student studentWithName:@”stu1”];
Student *stu2=[Student studentWithName:@”stu2”];
Student *stu3=[Student studentWithName:@”stu3”];
NSDictionary *dict=[NSDictionary dictoryWithObjectsAndKeys:
stu1,@”k1”,
stu2,@”k2”,
stu3,@”k3”,
,nil];
//when the dictionary is destroied key and value all released once
//但是字典不需我们销毁，注意是否是自动释放
}
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原文地址：http://www.cnblogs.com/yesihoang/p/4549423.html
