TypeChecking.md

Type Checking

ZIKRouter checks and limits the routing to make dynamic routing safer. The principle:

• Only routable protocol can be used for routing, or there will be complier errors
• If a protocol is routable, there must be a router for it

Compile-Time Checking

Swift

In Swift, use conditional extension to declare routable protocol, and let the compiler to check illegal usage.

See Routable Declaration.

Objective-C

In Objective-C, we use generic and macros to make compile time checking.

When registering and getting router with protocol, use macro ZIKRoutable to wrap the protocol:

@implementation EditorViewRouter

+ (void)registerRoutableDestination {
    [self registerView:[EditorViewController class]];
    
    //If the protocol is not inherited from ZIKViewRoutable, there will be compile warning
    [self registerViewProtocol:ZIKRoutable(EditorViewInput)];
}

@end

Use macro ZIKRouterToView, ZIKRouterToViewModule, ZIKRouterToService, ZIKRouterToServiceModule to get router class:

//If the protocol doesn't inherit from ZIKViewRoutable, there will be compile warning:
//'incompatible pointer types passing 'Protocol<UndeclaredProtocol> *' to parameter of type 'Protocol<ZIKViewRoutable> *'
ZIKRouterToView(UndeclaredProtocol)

You can setBuild Settings->Treat Incompatible Pointer Type Warnings as Errorsto YES.

And the protocol type will affect the parameters in methods:

//The 3 parameters have inheritance relationship
[ZIKRouterToView(EditorViewInput) //1
     performPath:ZIKViewRoutePath.pushFrom(self)
     strictConfiguring:^(ZIKViewRouteStrictConfiguration<id<EditorViewInput>> *config, //2
                         ZIKViewRouteConfiguration *module) {
         config.prepareDestination = ^(id<EditorViewInput> destination) { //3
         	   destination.delegate = weakSelf;
             destination.name = @"zuik";
             destination.age = 18;
         }
     }];

It's not 100% perfect like in Swift. If the protocol is changed to parent protocol, the compiler won't give any errors.

Runtime Checking

After auto registration is finished, ZIKRouter will check:

• All routers were registered with at least one destination class
• All protocols inheriting from ZIKViewRoutable,ZIKViewModuleRoutable,ZIKServiceRoutable,ZIKServiceModuleRoutable were registered with at least one router
• All swift protocols declared in extensions of RoutableView, RoutableViewModule, RoutableService, RoutableServiceModule were registered with at least one router
• If router is registered with a protocol, the router's destination or configuration must conforms to the protocol
• Even for a Swift type, ZIKRouter can also check it conformance with dynamic protocol types

For dynamically checking swift types, ZIKRouter uses private APIs in libswiftCore.dylib, and these code won't be compiled in release mode.

You can also do custom checking. In DEBUG mode, all routers' +_didFinishRegistration will be invoked when all registrations are finished. You can do custom checking here:

class SwiftSampleViewRouter: ZIKAnyViewRouter {
    ...
    override class func _didFinishRegistration() {
        // Custom checking
    }
    ...
}

Generic Parameter

The router subclass can set generic parameters when inheriting from ZIKViewRouter. There two generic parameters: Destination and RouteConfig.

class SwiftSampleViewRouter: ZIKViewRouter<SwiftSampleViewController, SwiftSampleViewConfiguration> {
    
    override class func registerRoutableDestination() {
        registerView(SwiftSampleViewController.self)
        register(RoutableView<PureSwiftSampleViewInput>())
        register(RoutableViewModule<SwiftSampleViewConfig>())
    }
    
    override class func defaultRouteConfiguration() -> SwiftSampleViewConfiguration {
        return SwiftSampleViewConfiguration()
    }
    
    override func destination(with configuration: SwiftSampleViewConfiguration) -> SwiftSampleViewController? {
        let sb = UIStoryboard.init(name: "Main", bundle: nil)
        let destination = sb.instantiateViewController(withIdentifier: "SwiftSampleViewController") as! SwiftSampleViewController
        return destination
    }
    
    override func prepareDestination(_ destination: SwiftSampleViewController, configuration: ZIKViewRouteConfiguration) {
        destination.injectedAlertRouter = Router.to(RoutableViewModule<ZIKCompatibleAlertConfigProtocol>())
    }
}

Generic parameters are just for indicating parameter type when overriding methods. So the generic parameters can be different from router's real destination or protocol.

Destination

Destination is type of router's destination.

RouteConfig

RouteConfig is type of router's configuration. You can use a custom type when using module config protocol.

Usage of Generic Parameters

Custom Swift generic doesn't support covariance and contravariance. So a ZIKViewRouter<UIViewController, ViewRouteConfig> type is not a ZIKViewRouter<AnyObject, ViewRouteConfig> type, there will be complie error if you assign one type to another. And OC class's generic parameters can't be pure swift types, therefore, we use ViewRouter and ServiceRouter to wrap ZIKViewRouter and ZIKServiceRouter, to support pure swift types.

Only one generic parameter will be set for each router. You can use convenient types like DestinationViewRouter,DestinationServiceRouter,ModuleViewRouter,ModuleServiceRouter. ViewRouter<EditorViewInput, ViewRouteConfig> can be replaced with DestinationViewRouter<EditorViewInput>.

When the router uses a module config protocol, the destination type can't be designated in generic parameter. If you want to designated destination type, you should return the destination in module config protocol's interface.

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