在這篇裡，我們要學習的目標：

1. 解析遠程的JSON數據
2. 分頁顯示數據
3. 學習Category的使用
概述

    IOS5.0開始支持JSON，所以不用第三方的解析了，主要用於這三個對象：NSDictionary、NSData、NSJSONSerializatio

今天我們做一個天氣預報數據的展示，通過國家氣象局提供的天氣預報接口來獲取數據。注：以實現功能為主，不做過多的界面上展示
  
View Code

 1 {
 2     "weatherinfo":{
 3         "city":"北京",
 4         "city_en":"beijing",
 5         "date_y":"2012年9月5日",
 6         "date":"",
 7         "week":"星期三",
 8         "fchh":"11",
 9         "cityid":"101010100",
10         "temp1":"27℃~17℃",
11         "temp2":"24℃~17℃",
12         "temp3":"25℃~17℃",
13         "temp4":"27℃~16℃",
14         "temp5":"28℃~17℃",
15         "temp6":"26℃~17℃",
16         "tempF1":"80.6℉~62.6℉",
17         "tempF2":"75.2℉~62.6℉",
18         "tempF3":"77℉~62.6℉",
19         "tempF4":"80.6℉~60.8℉",
20         "tempF5":"82.4℉~62.6℉",
21         "tempF6":"78.8℉~62.6℉",
22         "weather1":"晴轉陰",
23         "weather2":"陣雨",
24         "weather3":"陣雨轉多雲",
25         "weather4":"多雲轉晴",
26         "weather5":"晴",
27         "weather6":"多雲轉陣雨",
28         "img1":"0",
29         "img2":"2",
30         "img3":"3",
31         "img4":"99",
32         "img5":"3",
33         "img6":"1",
34         "img7":"1",
35         "img8":"0",
36         "img9":"0",
37         "img10":"99",
38         "img11":"1",
39         "img12":"3",
40         "img_single":"0",
41         "img_title1":"晴",
42         "img_title2":"陰",
43         "img_title3":"陣雨",
44         "img_title4":"陣雨",
45         "img_title5":"陣雨",
46         "img_title6":"多雲",
47         "img_title7":"多雲",
48         "img_title8":"晴",
49         "img_title9":"晴",
50         "img_title10":"晴",
51         "img_title11":"多雲",
52         "img_title12":"陣雨",
53         "img_title_single":"晴",
54         "wind1":"微風",
55         "wind2":"微風",
56         "wind3":"微風",
57         "wind4":"微風",
58         "wind5":"微風",
59         "wind6":"微風",
60         "fx1":"微風",
61         "fx2":"微風",
62         "fl1":"小於3級",
63         "fl2":"小於3級",
64         "fl3":"小於3級",
65         "fl4":"小於3級",
66         "fl5":"小於3級",
67         "fl6":"小於3級",
68         "index":"暖",
69         "index_d":"較涼爽，建議著長袖襯褲等春秋過渡裝。體弱者宜著長袖襯衫和馬甲。但晝夜溫差較大，請適當增減衣服。",
70         "index48":"暖",
71         "index48_d":"較涼爽，建議著長袖襯衫加單褲等春秋過渡裝。年老體弱者宜著針織長袖襯衫、馬甲和長褲。",
72         "index_uv":"中等",
73         "index48_uv":"弱",
74         "index_xc":"不宜",
75         "index_tr":"適宜",
76         "index_co":"較舒適",
77         "st1":"26",
78         "st2":"17",
79         "st3":"22",
80         "st4":"16",
81         "st5":"23",
82         "st6":"17",
83         "index_cl":"適宜",
84         "index_ls":"適宜",
85         "index_ag":"易發"
86     }
87 }

    Category 是Objective-C 裡面最常用到的功能之一。簡單的講Category可以為已經存在的類增加方法，而不需要增加一個子類。而且，我們可以在不知道某個類內部實現的情況下，為該類增加方法。如果我們想增加某個框架(framework)中的類的方法，Category就非常有效。比如，今天的內容中，就想在NSDictionary上增加一個方法來直接處理URL遠程數據，後面有詳細代碼。  定義格式如下：

1     #import "類名.h" 
2     @interface 類名(類別名) 
3         //新方法的聲明 
4     @end