ios – 数组中的Swift闭包在Objective-c中变为nil

概述我创建了一个 objective-c方法,它将通过NSInvocation调用一个方法： typedef void (^ScriptingEmptyBlock)();typedef void (^ScriptingErrorBlock)(NSError *error);- (void)scripting_execute:(NSString *)operation withParams:(nul 我创建了一个 objective-c方法,它将通过NSInvocation调用一个方法：

typedef voID (^ScriptingEmptyBlock)();typedef voID (^ScriptingErrorBlock)(NSError *error);- (voID)scripting_execute:(Nsstring *)operation withParams:(nullable NSArray *)args {    SEL selector = [self scripting_selectorForOperation:operation];    Class class = [self class];    NSMethodSignature *signature = [class instanceMethodSignatureForSelector:selector];    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];    [invocation setSelector:selector];    [invocation setTarget:self];    for (int IDx = 0; IDx < args.count; IDx ++) {        ID arg = args[IDx];        [invocation setArgument:&arg atIndex:IDx + 2];    }    ScriptingEmptyBlock success = args[1];    // Breakpoint added on next line to test for nil    success(); // this is nil and would crash!    // (lldb) po args.count    // 3    // (lldb) po success    // Printing description of success:    // (ScriptingEmptyBlock) success = 0x0000000000000000    // (lldb) po args[1]    // (Function)    //[invocation getArgument:&success atIndex:2]; // also trIEd this and got nil as well    [invocation invoke];}

该方法采用“ *** 作”,通过在子类中重写scripting_selectorForOperation来转换为选择器,然后执行调用.

所有这些都有效,除非被调用的方法具有块参数,它们都是nil,我添加了我用注释描述的nil的测试,当试图从数组中读取闭包时它将是nil.

叫做：

let successClosure: ScriptingEmptyBlock = {                    print("Renamed product")                }let errorClosure: ScriptingErrorBlock = { error in                    print("Failed to rename product: \(error)")                }let params:[Any] = [ "testname",successClosure,errorClosure]object.scripting_execute (Scriptoperation.updateProductname.rawValue,withParams: params)

封闭为什么变成零？

解决方法 成功不是零(事实上,NSArray不能包含nils).如果你打印它像NSLog(@“％@”,成功);它会说(函数),而不是(null).如果你像NSLog(@“％@”,[成功类])那样打印它的类,它会说_SwiftValue.基本上,它是Swift值,桥接到Objective-C.

问题是对象成功指向的不是Objective-C块.它是一个Swift闭包,Swift闭包与Objective-C块不同.尝试使用调用它就好像它是一个Objective-C块导致未定义的行为.调试器中的po打印错误可能是因为它正在打印它,假设它是类型ScriptingEmptyBlock(块类型).如果你做po(ID)成功,它将打印(功能).

至于如何从Swift中明确地将Objective-C块放入数组中,我想出的唯一方法就是：

let params:[Any] = [ "testname",successClosure as (@convention(block) () -> VoID)!,errorClosure as (@convention(block) (NSError) -> VoID)!]object.scripting_execute (Scriptoperation.updateProductname.rawValue,withParams: params)

我不确定为什么有必要将函数类型放在！中,但它似乎不起作用.也许其他人可以找到更好的方法.

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