在iOS开发中，经常会用到网络请求。当收到服务器返回的数据后，想从中获取某个值的话，得使用objectForKey的方式取。这样感觉不是很方便，而且繁琐。

介绍KeyValueObjectMapping对象映射的使用。

下载地址：https://github.com/dchohfi/KeyValueObjectMapping

可以在项目使用的地方引用需要的类

#import "DCKeyValueObjectMapping.h"
#import "DCParserConfiguration.h"
#import "DCObjectMapping.h"
#import "DCArrayMapping.h"

Tweet类

#import <Foundation/Foundation.h>

@interface Tweet : NSObject

@property(nonatomic, strong) NSString *idStr;
@property(nonatomic, strong) NSString *text;
@property(nonatomic, strong) NSDate *createdAt;


@end


#import "Tweet.h"

@implementation Tweet

@end

User类

#import <Foundation/Foundation.h>

@interface User : NSObject

@property(nonatomic, strong) NSString *idStr;
@property(nonatomic, strong) NSString *name;
@property(nonatomic, strong) NSString *screenName;
@property(nonatomic, strong) NSString *location;
@property(nonatomic, strong) NSString *description1;
@property(nonatomic, strong) NSURL *url;
@property(nonatomic) BOOL protected;
@property(nonatomic, strong) NSDate *createdAt;

@property(nonatomic, strong) NSArray *tweets;

@end


#import "User.h"

@implementation User

@end

可以使用下面的方法测试，就会明白其中的使用方法了，哈哈。。。

//获取本地json数据代码
NSString *caminhoJson = [[NSBundle bundleForClass: [self class]] pathForResource:@"tweet" ofType:@"json"];
NSData *data = [NSData dataWithContentsOfFile:caminhoJson];
NSError *error;
NSDictionary *jsonParsed = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];

DCKeyValueObjectMapping的使用, tweet.json文件及代码如下

{
    "id_str": "27924446",
    "name": "Diego Chohfi",
    "screen_name": "dchohfi",
    "location": "São Paulo",
    "description1": "Instrutor na @Caelum, desenvolvedor de coração, apaixonado por música e cerveja, sempre cerveja.",
    "url": "http://about.me/dchohfi",
    "protected": false,
    "created_at": "Tue Mar 31 18:01:12 +0000 2009",
    "tweets": []
}


//示例代码:
DCKeyValueObjectMapping *parser = [DCKeyValueObjectMapping mapperForClass: [Tweet class]];

Tweet *tweet = [parser parseDictionary:jsonParsed];
NSLog(@"%@ - %@", tweet.idStr, tweet.name);

DCObjectMapping的使用, tweet.json文件及代码如下

{
    "id_str": 190957570511478800,
    "text": "Tweet text",
    "user": {
        "name": "Diego Chohfi",
        "screen_name": "dchohfi",
        "location": "São Paulo"
    }
}


//示例代码:
DCParserConfiguration *config = [DCParserConfiguration configuration];

DCObjectMapping *textToTweetText = [DCObjectMapping mapKeyPath:@"text" toAttribute:@"tweetText" onClass:[Tweet class]];
DCObjectMapping *userToUserOwner = [DCObjectMapping mapKeyPath:@"user" toAttribute:@"userOwner" onClass:[Tweet class]];

[config addObjectMapping:textToTweetText];
[config addObjectMapping:userToUserOwner];

DCKeyValueObjectMapping *parser = [DCKeyValueObjectMapping mapperForClass: [Tweet class]  andConfiguration:config];
Tweet *tweetParsed = [parser parseDictionary:jsonParsed];
NSLog(@"%@ - %@ - %@ - %@", tweetParsed.idStr, tweetParsed.tweetText, tweetParsed.userOwner.screenName, tweetParsed.userOwner.createdAt);

DCArrayMapping的使用, tweet.json文件及代码如下

{
    "id_str": "27924446",
    "name": "Diego Chohfi",
    "screen_name": "dchohfi",
    "location": "São Paulo",
    "description1": "Instrutor na @Caelum, desenvolvedor de coração, apaixonado por música e cerveja, sempre cerveja.",
    "url": "http://about.me/dchohfi",
    "protected": false,
    "created_at": "Tue Mar 31 18:01:12 +0000 2009",
    "tweets" : [
        {
            "created_at" : "Sat Apr 14 00:20:07 +0000 2012",
            "id_str" : 190957570511478784,
            "text" : "Tweet text"
        },
        {
            "created_at" : "Sat Apr 14 00:20:07 +0000 2012",
            "id_str" : 190957570511478784,
            "text" : "Tweet text"
        }
    ]
}


//示例代码:
DCArrayMapping *mapper = [DCArrayMapping mapperForClassElements:[Tweet class] forAttribute:@"tweets" onClass:[User class]];
DCParserConfiguration *config = [DCParserConfiguration configuration];
[config addArrayMapper:mapper];
DCKeyValueObjectMapping *parser = [DCKeyValueObjectMapping mapperForClass:[User class] andConfiguration:config];
User *user = [parser parseDictionary:jsonParsed];
NSLog(@"%@ - %@ - %@", [user.tweets[0] idStr], user.screenName, [user.tweets[0] createdAt]);