遍历数组时崩溃

Question

我试图简单地打印出数组的内容。

//initialization, ...

    NSArray *stockprices = [NSArray arrayWithObjects:@[stock1,stock2,stock3], nil];

    for (BNRStockHolding *stock in stockprices) {
//            says that there are 3 objects in stock and crashes.
//            tried to check -> isMemberOfClass:BNRStockHolding in an if before and got 'unexpected interface name'.
        NSLog(@"Purchase Price: %.02f \n Shares: %d \n Current Price: %.02f \n \n \n \n", [stock purchasePrice], [stock numberOfShares],[stock currentSharePrice]);

Answer 1

当您这样做时：

NSArray *stockprices = [NSArray arrayWithObjects:@[stock1, stock2, stock3], nil];
//is same as
NSArray *stockprices = [NSArray arrayWithObjects:[NSArray arrayWithObjects:stock1, stock2, stock3, nil], nil];
//or
NSArray *stockprices = [NSArray arrayWithObjects:[[NSArray alloc] initWithObjects:stock1, stock2, stock3, nil], nil];

因此，您基本上是在创建一个数组，其第0个元素是数组，因为@[stock1,stock2,stock3]本身会创建一个数组。

---

而是：

NSArray *stockprices = [NSArray arrayWithObjects:stock1, stock2, stock3, nil];

要么

NSArray *stockprices = @[stock1,stock2,stock3];

Answer 2

您将在此处使用代码创建一个数组数组：

 NSArray *stockprices = [NSArray arrayWithObjects:@[stock1,stock2,stock3], nil];

您可以简单地写：

NSArray *stockprices = @[stock1,stock2,stock3];

Answer 3

您正在数组中使用数组； 父数组有一个对象，子数组有三个库存对象。 如果您将获得[parentArray objectAtIndex：0]; 它将正常工作； 但是，如果您要执行[parentArray objectAtIndex：1]; 应用会崩溃，因为父数组只有一个对象。 它可以帮助您调查问题。