网络编程

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根据极客班iOS课程整理。

一. 创建网络连接

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1. 声明实现代理

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@interface LoginRequest()<NSURLConnectionDataDelegate>

@end

2. 创建网络链接

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NSString *URLString = @"http://urlAddress/login.json";
URLString = [NSString stringWithFormat:@"%@?username=%@&password=%@",   URLString,username, password];

// 给字符串编码为utf-8, 否则中文字符会"unsupported URL"
NSString *encodedURLString = [URLString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *URL = [NSURL URLWithString:encodedURLString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
request.HTTPMethod = @"GET";
request.timeoutInterval = 60;   //设置超时
request.cachePolicy = NSURLRequestReloadIgnoringLocalAndRemoteCacheData;
self.URLConnection = [[NSURLConnection alloc] initWithRequest:request
                                                         delegate:self
                                                 startImmediately:YES];

3. 实现代理

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3.1 获取连接状态，“statusCode == 200”表示成功

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
    if (httpResponse.statusCode == 200) { //success
        self.receivedData = [NSMutableData data];
    } else {
        // error methods
    }
}

3.2 从服务器获取数据

- (void)connection:(NSURLConnection *)connection
    didReceiveData:(NSData *)data
{
    [self.receivedData appendData:data];
}

3.3 加载完数据

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *string = [[NSString alloc] initWithData:self.receivedData
                                             encoding:NSUTF8StringEncoding];
    NSLog(@"%@", string);
}

3.4 出错

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error  

4. 网络请求

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4.1 同步请求

[NSURLConnection sendSynchronousRequest:<#(NSURLRequest *)#>
                          returningResponse:<#(NSURLResponse *__autoreleasing *)#>
                                      error:<#(NSError *__autoreleasing *)#>];

4.2 异步请求（默认）

[NSURLConnection sendAsynchronousRequest:<#(NSURLRequest *)#>
                                        queue:<#(NSOperationQueue *)#>
                            completionHandler:<#^(NSURLResponse *response, NSData *data, NSError *connectionError)handler#>

二. 解析数据

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1. JSON (Java Script Object Notation)

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apple提供了函数

id jsonDic = [NSJSONSerialization JSONObjectWithData:data
                                    options:NSJSONReadingAllowFragments
                                      error:&error];

注意：

• value不一定是string，使用时需要判断

    if ([[userId class] isSubclassOfClass:[NSString class]]) {
        user.userID = userId;
    }

2. XML

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2.1 解析方式

• SAX，遍历，apple支持，需要实现代理
• DOM，先把数据转换成树
  • TBXML，开源库

2.2 声明实现XML代理

<NSXMLParserDelegate>

2.3 实现代理方法

1.开始节点

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict

2.结束节点

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName

3.数据

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string

4.解析xml数据

NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
NSError *error = [parser parserError];
if (error) {
       ... 
} else {
        ...
        parser.delegate = self;
        [parser parse];  // 开始解析
        ...
}

2.4 节点重名的处理

<?xml version="1.0" encoding="UTF-8" ?>
<user>
    <id><![CDATA[00001]]></id>  
    <userName>zhangsan</userName>   
    <age>28</age> 
    <headImageUrl>http://pica.nipic.com/2007-11-09/2007119124413448_2.jpg</headImageUrl> 
    <address>
        <id>12345</id>
        <city>上海</city>
    </address>
</user>

如上，"id"有两个。发生这种情况的时候，需要由內向外进行处理。

在didStartElement代理方法中添加：

if ([elementName isEqualToString:@"address"]) {
        _address = [[BLAddress alloc] init];
}

在didEndElement代理方法中添加

if ([elementName isEqualToString:@"address"]) {
        _user.address = _address;
        _address = nil;
} else if ([elementName isEqualToString:@"id"]) {
        if (_address) {
            _address.cityID = _currentValue;
        } else {
            _user.userID = _currentValue;
}

在address节点之间发现“id”时，_address不是空的。而在address节点之外，_address是空的。根据_address是否为空就能判断当前应给哪个id赋值。

三. 全局变量

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3.1 创建全局类

@interface BLGlobal : NSObject

@property (nonatomic, strong) BLUser *user;

+ (BLGlobal *)shareGlobal;

@end

实现

static BLGlobal *global = nil;

@implementation BLGlobal


+ (BLGlobal *)shareGlobal
{
    if (global == nil) {
        global = [[BLGlobal alloc] init];
    }
    return global;
}

3.2 访问

[BLGlobal shareGlobal].user

3.3 其他

• XXFoundation.h, 存放宏定义、枚举等