尽管对象是 NSMutableDictionary，但“发送到不可变对象的变异方法”

Question

我正在使用 NSMutableDictionary 并遇到此错误：

'NSInternalInconsistencyException', reason: '-[__NSCFDictionary removeObjectForKey:]: mutating method sent to immutable object'

代码如下：

    // Turn the JSON strings/data into objects
    NSError *error;
    NSMutableDictionary *invoiceDictFromReq = [[NSMutableDictionary alloc] init];
//    invoiceDictFromReq = (NSMutableDictionary *)[NSJSONSerialization JSONObjectWithData:[request responseData] options:kNilOptions error:&error];
    invoiceDictFromReq = [NSMutableDictionary dictionaryWithDictionary:[NSJSONSerialization JSONObjectWithData:[request responseData] options:kNilOptions error:&error]];

NSLog(@"invoiceDictFromReq count: %i, key: %@, value: %@", [invoiceDictFromReq count], [invoiceDictFromReq allKeys], [invoiceDictFromReq allValues]);

// Get values and keys from JSON response
self.invoiceDict = [invoiceDictFromReq objectForKey:@"invoice"];
NSNumber *invoiceAmount = [self.invoiceDict objectForKey:@"amount"];
NSNumber *invoiceId = [self.invoiceDict objectForKey:@"id"];
NSNumber *invoiceNumber = [self.invoiceDict objectForKey:@"number"];
NSNumber *checkoutStarted = [self.invoiceDict objectForKey:@"checkoutStarted"];
NSNumber *checkoutCompleted = [self.invoiceDict objectForKey:@"checkoutCompleted"];
NSLog(@"amount: %@, id: %@, number: %@, started: %@, completed: %@", invoiceAmount, invoiceId, invoiceNumber, checkoutStarted, checkoutCompleted);

所有控制台日志都表明数据正常。这就是事情开始崩溃的地方。 我将invoiceDict 属性传递给下一个视图控制器：

// Pass the invoice to checkoutViewController
[checkoutViewController setInvoiceDict:self.invoiceDict];

在 CheckoutViewController.m 中：

    // Change invoice checkoutCompleted to true
//    [self.invoiceDict removeObjectForKey:@"checkoutCompleted"];
    [self.invoiceDict setObject:[NSNumber numberWithBool:YES] forKey:@"checkoutCompleted"];

错误位于[self.invoiceDict setObject...]。我确保我使用的所有字典都是NSMutableDictionary。我在代码中留下了一些注释掉的行来显示我尝试过的东西，但我碰了壁。我想我总是可以创建一个新字典。这是首选的方法吗？

Answer 1

NSJSONSerialization 默认返回不可变对象。以下是如何从解析器中获取可变字典：

• 使用选项NSJSONReadingMutableContainers

或

• 在结果上使用mutableCopy

Answer 2

您在 invoiceDictFromReq 中分配一个字典，接下来您将创建另一个字典，您将在那里创建内存泄漏。 删除该行

NSMutableDictionary *invoiceDictFromReq = [[NSMutableDictionary alloc] init];

但是您的问题是您正在创建一个 NSMutableDictionary，但您正在将 mutableDictionary 中的字典设置为 self.invoiceDict，这也不一定是 mutableDictionary。 换行

self.invoiceDict = [invoiceDictFromReq objectForKey:@"invoice"];

为

self.invoiceDict = [NSMutableDictionary dictionaryWithDictionary:[invoiceDictFromReq objectForKey:@"invoice"]];