Swizzlingメモ #CodePiece

CodePiece.swift

public override static func initialize() {
    struct Static {
        static var token: dispatch_once_t = 0
    }
    
    struct SwizzlingSelector {
        let original:Selector
        let swizzled:Selector
    }
    
    // make sure this isn't a subclass
    if self !== SomeClass.self {
        return
    }
    
    dispatch_once(&Static.token) {
        
        let selectors = [
            SwizzlingSelector(
                original: Selector("collectionView:shouldSelectItemAtIndexPath:"),
                swizzled: Selector("custom_collectionView:shouldSelectItemAtIndexPath:")
            ),
            SwizzlingSelector(
                original: Selector("viewDidLoad"),
                swizzled: Selector("custom_viewDidLoad")
            )
        ]
        
        for selector in selectors {
            let originalMethod = class_getInstanceMethod(self, selector.original)
            let swizzledMethod = class_getInstanceMethod(self, selector.swizzled)
            
            let didAddMethod = class_addMethod(self, selector.original, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))
            
            if didAddMethod {
                class_replaceMethod(self, selector.swizzled, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
            } else {
                method_exchangeImplementations(originalMethod, swizzledMethod);
            }
        }
    }
}