Objective-c 字典对象

　　oc 中的 NSDictionary 的作用同 java 中的字典类相同，提供了 “键－值”对的组合。比如，是用字典类实现对学生姓名和学号的存放，编号是一个键（唯一性），姓名是值。它的方法有：

　　

　　下面通过例子来具体说明它的用法：

　　 1）构建字典

　　

#import <Foundation/Foundation.h>

int main(int argc , const char *argv[]){
    @autoreleasepool{
        NSDictionary *dicti1 = [NSDictionary     dictionaryWithObjectsAndKeys:@"zhangsan",@"1",@"lisi",@"2",@"wangwu",@"3", nil];
        NSEnumerator *keynum = [dicti1 keyEnumerator];
        for(NSString *key in keynum)
            NSLog(@"key = %@ , value = %@",key,[dicti1 objectForKey:key]);
        
        NSLog(@"----------------------------");
        NSDictionary *dicti2 = [[NSDictionary alloc]initWithObjectsAndKeys:@"zhangsan",@"1",@"lisi",@"2",@"wangwu",@"3", nil];
        keynum = [dicti2 keyEnumerator];
        for(NSString *key in keynum)
            NSLog(@"key = %@ , value = %@",key,[dicti2 objectForKey:key]);
        
        NSLog(@"----------------------------");
        NSDictionary *dicti3 = @{@"1":@"zhangsan",@"2":@"lisi",@"3":@"wangwu"};
        keynum = [dicti3 keyEnumerator];
        for(NSString *key in keynum)
            NSLog(@"key = %@  , value = %@",key,[dicti3 objectForKey:key]);
        
        NSLog(@"------------------------------");
        NSArray *keyarray = @[@"1",@"2",@"3"];
        NSArray *valuearray = @[@"zhangsan",@"lisi",@"wangwu"];
        NSDictionary *dicti4 = [NSDictionary dictionaryWithObjects:valuearray forKeys:keyarray];
        keynum = [dicti4 keyEnumerator];
        for(NSString *key in keynum)
            NSLog(@"key = %@ , value = %@",key,[dicti4 objectForKey:key]);
        
    }
    return 0;
}

 　　

　　2）字典的遍历

　　

#import <Foundation/Foundation.h>

int main(int argc , const char *argv[]){
    @autoreleasepool {
        NSDictionary *dicti = [NSDictionary dictionaryWithObjectsAndKeys:@"zhangsan",@"1",@"lisi",@"2",@"wangwu",@"3", nil];
        NSEnumerator *number = [dicti keyEnumerator];
        for(NSString *key in number)
            NSLog(@"key = %@ , value = %@",key,[dicti objectForKey:key]);
        
        NSLog(@"----------------------------");
        NSArray *keyarray = [dicti allKeys];
        for(NSString *key in keyarray)
            NSLog(@"key = %@ , value = %@",key,[dicti objectForKey:key]);
        
        NSLog(@"-----------------------------");
        for(NSString *key in  dicti)
            NSLog(@"key = %@ , value = %@",key,[dicti objectForKey:key]);
        
        NSLog(@"-----------------------------");
        [dicti enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
            NSLog(@"key = %@  ,value = %@",key,obj);
        }];
    }
　　　　return 0;
}

3)  文件的读取

#import <Foundation/Foundation.h>

int main(int argc , const char *argv[]){
    @autoreleasepool {
        NSDictionary *dicti = [NSDictionary dictionaryWithObjectsAndKeys:@"zhangsan",@"1",@"lisi",@"2",@"wangnwu",@"3",nil];
        
        NSString *filename = @"dicti.txt";
        BOOL iswrite = [dicti writeToFile:filename atomically:YES];
        if(iswrite)
            NSLog(@"write to file ok");
        else
            NSLog(@"write to file error");
        
        NSDictionary *dicti2 = [NSDictionary dictionaryWithContentsOfFile:filename];
        NSLog(@"dicti2 = %@",dicti2);
        
    }
　　　　return 0;
}

　　4） 查找

　　

#import <Foundation/Foundation.h>

int main(int argc , const char *argv[])
{
    @autoreleasepool {
        NSDictionary  *dicti = [NSDictionary dictionaryWithObjectsAndKeys:@"zhangsan",@"1",@"lisi",@"2",@"wangwu",@"3",@"zhangsan",@"4",nil];
        
        NSArray *keyarray = [dicti allKeys];     // 查找所有键值
        NSLog(@"%@",keyarray);
        
        NSArray *valuearray = [dicti allValues];  // 查找所有值
        NSLog(@"%@",valuearray);
        
        NSString *value = [dicti objectForKey:@"1"];   // 按键值查找
        NSLog(@"value = %@",value);
        
        value = dicti[@"2"];
        NSLog(@"value = %@",value);
        
        NSArray *keyarray2 = @[@"1",@"2",@"3"];    // 利用数组的方式查找
        NSArray *vlauearray2 = [dicti objectsForKeys:keyarray2 notFoundMarker:@"nil"];
        NSLog(@"vlauearray2 = %@",vlauearray2);
        
        NSArray *keyarray3 = [dicti allKeysForObject:@"zhangsan"];
        NSLog(@"keyarray3 = %@",keyarray3);
        
        NSDictionary *dicti2 = [dicti dictionaryWithValuesForKeys:keyarray2];
        NSLog(@"dicti2 = %@",dicti2);
    }
    return 0;
}

 5) 排序

　　

#import <Foundation/Foundation.h>


int main(int argc,char **argv){
    @autoreleasepool {
        NSDictionary *dicti = [NSDictionary dictionaryWithObjectsAndKeys:@"zhangsan",@"2",@"lisi",@"3",@"wangwu",@"1",@"zhangsan",@"4",nil];
        NSLog(@"dicti = %@",dicti);
        
        NSDictionary *dicti2 = [NSDictionary dictionaryWithObjectsAndKeys:@"zhangsan",@1,@"lisi",@2,@"wangu",@3, nil];
        NSLog(@"dicti2 = %@",dicti2);
        
        NSArray *array = [dicti2 keysSortedByValueUsingSelector:@selector(compare:)];
        for(NSNumber *key in array)
            NSLog(@"key = %@,value = %@",key,dicti2[key]);
    }
    return 0;
}

　　2. 同样字典对象中也存在可变字典（NSDictionary）,下面我们来通过一个例子来说明它的用法：

　　

　　代码举例：

　　

#import <Foundation/Foundation.h>


int main(int argc,char **argv){
    @autoreleasepool {
        NSMutableDictionary *mdicti = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"zhangsan",@"1",@"lisi",@"2",@"wangwu",@"3",nil];
        
        [mdicti setValue:@"zhaoliu" forKey:@"4"];    // 如果 key 不存在就添加，key 存在就修改
        NSLog(@"mdicti = %@",mdicti);
        
        [mdicti setValue:@"zzz" forKey:@"1"];
        NSLog(@"mdicti = %@",mdicti);
        
        mdicti[@"5"] = @"bbb";
        NSLog(@"mdicti = %@",mdicti);
        
        NSDictionary *dicti = [NSDictionary dictionaryWithObjectsAndKeys:@"aaa",@"11",@"bbb",@"12",@"ccc",@"13",nil];
        [mdicti addEntriesFromDictionary:dicti];
        NSLog(@"dicti = %@",mdicti);
        
        [mdicti removeObjectForKey:@"1"];     // 删除
        NSLog(@"mdicti = %@",mdicti);
        
        NSArray *array = @[@"11",@"12",@"13"];
        [mdicti removeObjectsForKeys:array];
        NSLog(@"mdicti = %@",mdicti);
        
        [mdicti removeAllObjects];  // 删除所有的
        NSLog(@"%@",mdicti);
    }
    return 0;
}