ios - 将 objective-c 协议(protocol)委托(delegate)作为参数传递

Question

当我将 objective-c 协议(protocol)作为参数传递时，然后使用该委托(delegate)来触发其方法之一时，该方法不会触发。

我正在使用来自 Paypal iOS SDK 的委托(delegate)定义如下:

@protocol PayPalPaymentDelegate <NSObject>
    - (void)payPalPaymentDidCancel:(PayPalPaymentViewController *)paymentViewController;
@end

我有一个实现协议(protocol)的 UIViewController:

//simpleviewcontroller.h
@interface SimpleViewController : UIViewController<PayPalPaymentDelegate>

和如下所示的方法签名:

// HelperFunctions.m
+ (void) doSomething: (id<PayPalPaymentDelegate>)paypalDelegate
{
    // the selector 'payPalPaymentDidCancel' DOES fire
    [paypalDelegate performSelector:@selector(payPalPaymentDidCancel:) withObject:self]
}


// called from simpleviewcontroller.m that implements PayPalPaymentDelegate
[HelperFunctions doSomething: self]

问题是paypal返回结果的时候，没有触发委托(delegate):

// code inside of the 'success' block of an AFNetworking call
PayPalPaymentViewController *paymentViewController;
paymentViewController = [[PayPalPaymentViewController alloc] initWithPayment:payment    
                                                             configuration:paypalConfiguration   
                                                             delegate:paypalDelegate];

这里传递给'delegate'的paypalDelegate永远不会被paypal触发。而如果从 simpleviewcontroller.m 完成而不是通过方法 doSomething 则触发它

Answer 1

一旦您创建了 paymentViewController，您是否在某处保留了 paypalDelegate？ PayPalPaymentViewController 仅保留对委托(delegate)的弱引用，因此如果没有，它将在创建 PayPalPaymentViewController.