iOS App

iOS App For Myself.

Hosts

在开发过程中，经常需要修改Hosts访问测试环境，而对于非越狱iOS设备，无法修改设备Host文件/etc/hosts;如果在代码中直接将域名修改为ip地址，存在两个问题：

  1. 破坏了网络代码的结构。
  2. HTTP Header中的”Host”字段也被修改为了ip地址，而后台对”Host”字段有校验,会导致请求出错。

可以通过对NSURLRequest的initWithURL:cachePolicy:timeoutInterval:方法和NSMutableURLRequest的setURL:方法进行 method swizzle来动态的将URL中的host修改为ip,并保持HTTP Header中的”Host”字段不变来解决。

使用NLHosts类来保存host到ip的转换

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interface NLHosts : NSObject

+(NSString*)ipByHost:(NSString*)host;

@end

+ipByHost:方法接收host参数，如果对应host有匹配的ip地址,则返回ip地址，否则返回nil。

NSURLRequest、NSMutableURLRequest的method swizzle处理

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@interface NSURLRequest (Swizzle)

@end


@interface NSMutableURLRequest (Swizzle)

@end
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#import "NSURLRequest+Swizzle.h"

#import <objc/runtime.h>
#import "NLHosts.h"

@implementation NSURLRequest (Swizzle)

+(void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class clazz = NSClassFromString(@"NSURLRequest");
        Method origMethod = class_getInstanceMethod(clazz, @selector(initWithURL:cachePolicy:timeoutInterval:));
        Method newMethod = class_getInstanceMethod(clazz, @selector(initWithNewURL:cachePolicy:timeoutInterval:));

        if (origMethod && newMethod) {
            method_exchangeImplementations(origMethod, newMethod);
        }else{
            //NSLog(@"origMethod:%@ newMethod:%@",origMethod,newMethod);
        }
    });
}

-(id)initWithNewURL:(NSURL *)URL cachePolicy:(NSURLRequestCachePolicy)cachePolicy timeoutInterval:(NSTimeInterval)timeoutInterval
{
    NSString *scheme = URL.scheme;

    if ([scheme compare:@"http" options:NSCaseInsensitiveSearch] == NSOrderedSame || [scheme compare:@"https" options:NSCaseInsensitiveSearch] == NSOrderedSame) {
        NSString *host = URL.host;
        NSString *ip = [NLHosts ipByHost:host];
        if (ip) {
            //NSLog(@"NSURLRequest: host:%@->ip:%@",host,ip);
            NSString *absoluteString = [URL absoluteString];
            NSRange hostRange = [absoluteString rangeOfString:host];
            if (hostRange.location != NSNotFound) {
                absoluteString = [absoluteString stringByReplacingCharactersInRange:hostRange withString:ip];
                NSURL *newURL = [NSURL URLWithString:absoluteString];
                NSMutableURLRequest *newRequest = [[NSMutableURLRequest alloc]initWithURL:newURL cachePolicy:cachePolicy timeoutInterval:timeoutInterval];
                [newRequest setValue:host forHTTPHeaderField:@"Host"];
                self = newRequest;
                return self;
            }
        }
    }
    return [self initWithNewURL:URL cachePolicy:cachePolicy timeoutInterval:timeoutInterval];
}

@end


@implementation NSMutableURLRequest (Swizzle)

+(void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class clazz = NSClassFromString(@"NSMutableURLRequest");
        Method origMethod = class_getInstanceMethod(clazz, @selector(setURL:));
        Method newMethod = class_getInstanceMethod(clazz, @selector(setNewURL:));

        if (origMethod && newMethod) {
            method_exchangeImplementations(origMethod, newMethod);
        }else{
            NSLog(@"origMethod:%@ newMethod:%@",origMethod,newMethod);
        }
    });
}

-(void)setNewURL:(NSURL *)URL
{
    NSString *scheme = URL.scheme;

    if ([scheme compare:@"http" options:NSCaseInsensitiveSearch] == NSOrderedSame || [scheme compare:@"https" options:NSCaseInsensitiveSearch] == NSOrderedSame) {
        NSString *host = URL.host;
        NSString *ip = [NLHosts ipByHost:host];
        if (ip) {
            //NSLog(@"NSMutableURLRequest setURL: host:%@->ip:%@",host,ip);
            NSString *absoluteString = [URL absoluteString];
            NSRange hostRange = [absoluteString rangeOfString:host];
            if (hostRange.location != NSNotFound) {
                absoluteString = [absoluteString stringByReplacingCharactersInRange:hostRange withString:ip];
                NSURL *newURL = [NSURL URLWithString:absoluteString];
                [self setNewURL:newURL];
                [self setValue:host forHTTPHeaderField:@"Host"];
                return;
            }
        }
    }

    return [self setNewURL:URL];

}


@end

在NSURLRequest类的+load方法中将-initWithURL:cachePolicy:timeoutInterval:替换为initWithNewURL:cachePolicy:timeoutInterval:;

在initWithNewURL:cachePolicy:timeoutInterval:方法中，如果初始化URL中的host需要转换为ip地址，则使用ip地址替换host生成新的URL,使用新URL生成新的 NSMutableURLRequest,并设置其HTTP Header的”Host”字段为原始值，将此NSMutableURLRequest返回进行后续网络请求。

NSMutableURLRequest是NSURLRequest的子类，所以初始化方法在NSURLRequest中进行method swizzle替换后，同样可适用在NSMutableURLRequest。 这样在initWithNewURL:cachePolicy:timeoutInterval:中生成新的NSMutableURLRequest时同样也会调用swizzle过的初始化方法，但此时的 host已经是ip地址了，不需要再次进行转换，会直接调用原方法返回。

对NSMutableURLRequest类的-setURL:方法也需要进行类似的处理,具体见代码。