MGJRouter程式碼分析

今天來聊聊元件化，之前一直聽說大廠在搞，什麼淘寶架構，什麼蘑菇街，既然談到了架構的問題，那必屬重中之重。接下來分析一下蘑菇街開源的程式碼，自己做個總結。

引入

類書本的文章個人感覺還是寫不來的，再搬到自己寫的東西這來也不合適，所以直接上一連結，通過連結文章大致可瞭解下它的前身後世，產生原因，以及整體巨集觀架構設計，而我接下來要做的是細化，以及轉化，便於自己吸收 ---------> 元件化架構漫談

1. 話不多說，先看入口：

@interface MGJRouter ()
/**
 *  儲存了所有已註冊的 URL
 *  結構類似 @{@"beauty": @{@":id": {@"_", [block copy]}}}
 */
@property (nonatomic) NSMutableDictionary *routes;
@end

+ (instancetype)sharedInstance
{
    static MGJRouter *instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}

很明顯，蘑菇街架構（以下簡稱MGJ）通過該單例作管理，統一進行調配，而該單例僅有一個變數，就是routes，實際上它僅僅是管理了一個字典的結構，具體字典內有哪些內容，我們慢慢看；

2. 回撥Block的定義

/**
 *  routerParameters 裡內建的幾個引數會用到上面定義的 string
 */
typedef void (^MGJRouterHandler)(NSDictionary *routerParameters);

/**
 *  需要返回一個 object，配合 objectForURL: 使用
 */
typedef id (^MGJRouterObjectHandler)(NSDictionary *routerParameters);

上面這兩個block定義是MGJ註冊URL的回撥，一個帶返回值，另一個不帶，在這裡我們說一下帶返回值的block用法；如下舉例 ------>

//宣告
typedef UIViewController *(^ViewControllerHandler)();

//作引數
@interface DemoListViewController : UIViewController
+ (void)registerWithTitle:(NSString *)title handler:(ViewControllerHandler)handler;
@end

//定義
@implementation DemoListViewController
+ (void)registerWithTitle:(NSString *)title handler:(ViewControllerHandler)handler
{
    UIViewController* vc = handler()
}
@end

//在別處呼叫
@implementation DemoDetailViewController
[DemoListViewController registerWithTitle:@"基本使用" handler:^UIViewController *{
        return DemoDetailViewController();
}];
@end

如上，我們把ViewControllerHandler的執行延遲到了實際呼叫的時刻，並且我們可以在這個handler的實現中帶入很多資訊；

3. MGJ資料結構管理

extern NSString *const MGJRouterParameterURL;
extern NSString *const MGJRouterParameterCompletion;
extern NSString *const MGJRouterParameterUserInfo;
//*************************************************
static NSString * const MGJ_ROUTER_WILDCARD_CHARACTER = @"~";  //這是一個佔位符
static NSString *specialCharacters = @"/?&.";

NSString *const MGJRouterParameterURL = @"MGJRouterParameterURL";
NSString *const MGJRouterParameterCompletion = @"MGJRouterParameterCompletion";
NSString *const MGJRouterParameterUserInfo = @"MGJRouterParameterUserInfo";

從這裡我們可以看出，MGJ的路由管理，實際上是一個解析url以及對應的管理，我們舉幾個URL來看一下：

@"mgj://"
@"mgj://foo/bar/none/exists"
@"mgj://foo/bar" 
@"mgj://category/家居"
@"mgj://category/travel"
@"mgj://search/:query"
@"mgj://detail"
@"mgj://search/:keyword"
@"mgj://search_top_bar"

通過上面的URL我們可以看出，路由的管理實際上就是url的解析過程，下面我們來具體看一下解析過程；

4. URL解析

• route url

- (NSArray*)pathComponentsFromURL:(NSString*)URL
{
    NSMutableArray *pathComponents = [NSMutableArray array];
    if ([URL rangeOfString:@"://"].location != NSNotFound) {
        NSArray *pathSegments = [URL componentsSeparatedByString:@"://"];
        // 如果 URL 包含協議，那麼把協議作為第一個元素放進去
        [pathComponents addObject:pathSegments[0]];
        
        // 如果只有協議，那麼放一個佔位符
        URL = pathSegments.lastObject;
        if (!URL.length) {
            [pathComponents addObject:MGJ_ROUTER_WILDCARD_CHARACTER];
        }
    }

    for (NSString *pathComponent in [[NSURL URLWithString:URL] pathComponents]) {
        if ([pathComponent isEqualToString:@"/"]) continue;
        if ([[pathComponent substringToIndex:1] isEqualToString:@"?"]) break;
        [pathComponents addObject:pathComponent];
    }
    return [pathComponents copy];
}

• key-value

  
  
  WX20180107-151956@2x.png-111.8kB

- (NSMutableDictionary *)addURLPattern:(NSString *)URLPattern
{
    NSArray *pathComponents = [self pathComponentsFromURL:URLPattern];

    NSMutableDictionary* subRoutes = self.routes;
    
    for (NSString* pathComponent in pathComponents) {
        if (![subRoutes objectForKey:pathComponent]) {
            subRoutes[pathComponent] = [[NSMutableDictionary alloc] init];
        }
        subRoutes = subRoutes[pathComponent];
    }
    return subRoutes;
}

• 核心url解析

- (NSMutableDictionary *)extractParametersFromURL:(NSString *)url
{
    NSMutableDictionary* parameters = [NSMutableDictionary dictionary];
    
    parameters[MGJRouterParameterURL] = url;
    
    NSMutableDictionary* subRoutes = self.routes;
    NSArray* pathComponents = [self pathComponentsFromURL:url];
    
    BOOL found = NO;
    // borrowed from HHRouter(https://github.com/Huohua/HHRouter)
    for (NSString* pathComponent in pathComponents) {
        
        // 對 key 進行排序，這樣可以把 ~ 放到最後
        NSArray *subRoutesKeys =[subRoutes.allKeys sortedArrayUsingComparator:^NSComparisonResult(NSString *obj1, NSString *obj2) {
            return [obj1 compare:obj2];
        }];
        
        for (NSString* key in subRoutesKeys) {
            if ([key isEqualToString:pathComponent] || [key isEqualToString:MGJ_ROUTER_WILDCARD_CHARACTER]) {
                found = YES;
                subRoutes = subRoutes[key];
                break;
            } else if ([key hasPrefix:@":"]) {
                found = YES;
                subRoutes = subRoutes[key];
                NSString *newKey = [key substringFromIndex:1];
                NSString *newPathComponent = pathComponent;
                // 再做一下特殊處理，比如 :id.html -> :id
                if ([self.class checkIfContainsSpecialCharacter:key]) {
                    NSCharacterSet *specialCharacterSet = [NSCharacterSet characterSetWithCharactersInString:specialCharacters];
                    NSRange range = [key rangeOfCharacterFromSet:specialCharacterSet];
                    if (range.location != NSNotFound) {
                        // 把 pathComponent 後面的部分也去掉
                        newKey = [newKey substringToIndex:range.location - 1];
                        NSString *suffixToStrip = [key substringFromIndex:range.location];
                        newPathComponent = [newPathComponent stringByReplacingOccurrencesOfString:suffixToStrip withString:@""];
                    }
                }
                parameters[newKey] = newPathComponent;
                break;
            }
        }
        
        // 如果沒有找到該 pathComponent 對應的 handler，則以上一層的 handler 作為 fallback
        if (!found && !subRoutes[@"_"]) {
            return nil;
        }
    }
    
    // Extract Params From Query.
    NSArray<NSURLQueryItem *> *queryItems = [[NSURLComponents alloc] initWithURL:[[NSURL alloc] initWithString:url] resolvingAgainstBaseURL:false].queryItems;
    
    for (NSURLQueryItem *item in queryItems) {
        parameters[item.name] = item.value;
    }

    if (subRoutes[@"_"]) {
        parameters[@"block"] = [subRoutes[@"_"] copy];
    }
    
    return parameters;
}

+ (void)openURL:(NSString *)URL withUserInfo:(NSDictionary *)userInfo completion:(void (^)(id result))completion
{
    URL = [URL stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSMutableDictionary *parameters = [[self sharedInstance] extractParametersFromURL:URL];
    
    [parameters enumerateKeysAndObjectsUsingBlock:^(id key, NSString *obj, BOOL *stop) {
        if ([obj isKindOfClass:[NSString class]]) {
            parameters[key] = [obj stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        }
    }];
    
    if (parameters) {
        MGJRouterHandler handler = parameters[@"block"];
        if (completion) {
            parameters[MGJRouterParameterCompletion] = completion;
        }
        if (userInfo) {
            parameters[MGJRouterParameterUserInfo] = userInfo;
        }
        //所以註冊路由時的回撥是在這裡才呼叫到的
        //也就是openURL響應了register的回撥
        if (handler) {
            [parameters removeObjectForKey:@"block"];
            handler(parameters);
        }
    }
}

5. 後續？