Question

我试图调用一个带有多个（2+）参数的选择器（可以确定参数的数量）。但是，选择器在编译时是未知的（实际上是使用NSSelectorFromString生成的）。

在Objective-C中，我可以创建一个调用并为其设置参数并调用它。但这在Swift中不可用。有没有办法解决？像：

let obj = SomeClass()
let selector = NSSelectorFromString("arg1:arg2:arg3:") //selector, arguments known only at runtime
//invoke selector

Answer 1

Swift 3.1

NSInvocation可以动态使用，但仅作为有趣的练习，绝对不适用于严肃的应用程序。还有更好的alternatives。

class Test : NSObject
{
    var name : String? {
        didSet {
            NSLog("didSetCalled")
        }
    }

    func invocationTest() {
        let invocation : NSObject = unsafeBitCast(method_getImplementation(class_getClassMethod(NSClassFromString("NSInvocation"), NSSelectorFromString("invocationWithMethodSignature:"))),to:(@convention(c)(AnyClass?,Selector,Any?)->Any).self)(NSClassFromString("NSInvocation"),NSSelectorFromString("invocationWithMethodSignature:"),unsafeBitCast(method(for: NSSelectorFromString("methodSignatureForSelector:"))!,to:(@convention(c)(Any?,Selector,Selector)->Any).self)(self,NSSelectorFromString("methodSignatureForSelector:"),#selector(setter:name))) as! NSObject
        unsafeBitCast(class_getMethodImplementation(NSClassFromString("NSInvocation"), NSSelectorFromString("setSelector:")),to:(@convention(c)(Any,Selector,Selector)->Void).self)(invocation,NSSelectorFromString("setSelector:"),#selector(setter:name))
        var localName = name
        withUnsafePointer(to: & localName) { unsafeBitCast(class_getMethodImplementation(NSClassFromString("NSInvocation"), NSSelectorFromString("setArgument:atIndex:")),to:(@convention(c)(Any,Selector,OpaquePointer,NSInteger)->Void).self)(invocation,NSSelectorFromString("setArgument:atIndex:"), OpaquePointer($0),2) }
        invocation.perform(NSSelectorFromString("invokeWithTarget:"), with: self)
    }
}

Answer 2

我担心在Swift中无法做到这一点。

但是，您可能有一个Objective-C类来管理动态调用。您可以在那里使用NSInvocation。

在Swift中有没有NSInvocation的替代方案？

2 个答案: