Ios 修改NSObjects的内部属性（特别是SKPaymentTransaction）

我正在尝试对我们的收据验证服务器进行单元测试，虽然我可以修改内部API以避免此问题，但这意味着我们没有完全测试客户端API，因此我希望避免这种情况

作为API的一部分，我们先传递一个SKPaymentTransaction，然后将Transaction.TransactionReceive传递到服务器

为了正确测试这一点，我想创建一个SKPaymentTransaction实例，并选择TransactionReceive（有效值和无效值）

不幸的是，SKPaymentTransaction将transactionReceipt属性定义为只读，并且我无法声明将其定义为readwrite的扩展/子类

我似乎也无法将SKPaymentTransaction指针强制转换为char*来手动将值注入内存，因为Xcode在ARC下不允许这样做

有没有人知道我如何才能实现我的目标

谢谢

---

Lee

发现我可以通过swizzle transactionReceipt getter将我自己的数据注入到调用中

所以我的结局是

-(void)test_function
{
    SKPaymentTransaction* invalidTransaction = [[SKPaymentTransaction alloc] init];

    Method swizzledMethod = class_getInstanceMethod([self class], @selector(replaced_getTransactionReceipt));
    Method originalMethod = class_getInstanceMethod([invalidTransaction class], @selector(transactionReceipt));

    method_exchangeImplementations(originalMethod, swizzledMethod);

    // Call to receipt verification server
}

- (NSData*)replaced_getTransactionReceipt
{
    return [@"blah" dataUsingEncoding:NSUTF8StringEncoding];
}

我写了一篇博客文章，展示了我的过程，并在这里提供了更多细节。

---

I子类SKPaymentTransaction（例如MutableSKPaymentTransaction），覆盖只读参数。已经有一个可变的SKPaymentTransaction，您可以使用它，也可以用类似的方式覆盖SKPayment

例如：

在头文件（MutableSKPaymentTransaction.h）文件中

#import <StoreKit/StoreKit.h>

@interface MutableSKPaymentTransaction : SKPaymentTransaction

@property (readwrite, copy, nonatomic) NSError * error;
@property (readwrite, copy, nonatomic) SKPayment * payment;
@property (readwrite, copy, nonatomic) NSString * transactionIdentifier;
@property (readwrite, copy, nonatomic) NSDate * transactionDate;
@property (readwrite, copy, nonatomic) NSArray * downloads;
@property (readwrite, copy, nonatomic) SKPaymentTransaction *originalTransaction;
@property (assign, nonatomic) SKPaymentTransactionState transactionState;

@end

#import "MutableSKPaymentTransaction.h"

@implementation MutableSKPaymentTransaction

// readonly override
@synthesize error = _error;
@synthesize payment = _payment;
@synthesize transactionIdentifier = _transactionIdentifier;
@synthesize transactionDate = _transactionDate;
@synthesize downloads = _downloads;
@synthesize originalTransaction = _originalTransaction;
@synthesize transactionState = _transactionState;

@end