Question

我对释放我首先分配/初始化然后复制的对象感到困惑。据我所知，内存管理手册我应该释放对象2次，因为通过分配它然后再复制它我应该保留2的值？那么第一次发布会将它降低到1，然后再降低到0？如果我发布两次，我会将消息发送到dealloc对象。如果我这样做，一旦申请没有问题，但我对Objetive C mem的理解有一个。管理：）））

我能想到的唯一解释是当你从一个特定的上下文中释放一个对象时，它会立即释放它，无论保留计数的值是什么？

在下面的代码片段中，xmlElement令人困惑....

// LSnippet of code for TouchXML
for (CXMLElement *resultElement in resultNodes) {

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

    // Create a counter variable as type "int"
    int counter;

    // Loop through the children of the current  node
    for(counter = 0; counter < [resultElement childCount]; counter++) {

        // Add each field to the blogItem Dictionary with the node name as key and node value as the value
        [xmlElement setObject:[[resultElement childAtIndex:counter] stringValue] forKey:[[resultElement childAtIndex:counter] name]];
    }

    // Add the blogItem to the global blogEntries Array so that the view can access it.


    [tempReturnedElements addObject:[xmlElement copy]];
    [xmlElement release];    
    //[xmlElement release]; but NOT!


}

更新：整个方法代码：

+(void) runXPath:(NSString *)xPathExpression{

CXMLDocument *rssParser = [[[CXMLDocument alloc] initWithXMLString:xmlStringContent options:0 error:nil] autorelease];

// Create a new Array object to be used with the looping of the results from the rssParser
NSArray *resultNodes = NULL;


// Set the resultNodes Array to contain an object for every instance of an  node in our RSS feed
resultNodes = [rssParser nodesForXPath:xPathExpression error:nil];

NSMutableArray *tempReturnedElements = [[NSMutableArray alloc]init];

// Loop through the resultNodes to access each items actual data
for (CXMLElement *resultElement in resultNodes) {

    // Create a temporary MutableDictionary to store the items fields in, which will eventually end up in blogEntries
    NSMutableDictionary *xmlElement = [[NSMutableDictionary alloc] init];

    // Create a counter variable as type "int"
    int counter;

    // Loop through the children of the current  node
    for(counter = 0; counter < [resultElement childCount]; counter++) {

        // Add each field to the blogItem Dictionary with the node name as key and node value as the value
        [xmlElement setObject:[[resultElement childAtIndex:counter] stringValue] forKey:[[resultElement childAtIndex:counter] name]];
    }

    // Add the blogItem to the global blogEntries Array so that the view can access it.


    [tempReturnedElements addObject:[xmlElement copy]];
//***** Crushes if I use:
//***** [tempReturnedElements addObject:[[xmlElement copy] autorelease]];
    [xmlElement release];



}


[lotojuegosAppDelegate setMyReturnedXmlElements:[tempReturnedElements copy]];

[tempReturnedElements release];

}

提前致谢，卢卡

Answer 1

在[xmlElement copy]中，只需要释放返回的对象（即副本）。接收方（xmlElement）的所有权（保留计数）不会更改。

所以正确的方法应该是

    NSDictionary* xmlElemCopy = [xmlElement copy];
    [tempReturnedElements addObject:xmlElemCopy];
    [xmlElemCopy release];
    [xmlElement release];

Answer 2

规则非常简单：对于每个alloc/init，copy或retain，当您想要放弃时，您必须只调用一个release或autorelease所有权。您只拨打了一个alloc/init，因此您只能拨打release一次。

这一行：

[tempReturnedElements addObject:[xmlElement copy]];

应写成：

[tempReturnedElements addObject:[[xmlElement copy] autorelease]];

原因是：copy为您提供了一个新对象。 xmlElement指向的对象的保留计数/所有权未更改，但新对象现在属于您。你现在负责释放它。请参阅本答案中的第一段：您调用了copy，您需要在生成的对象上调用release。

释放2次？

2 个答案: