可能的保留周期 - iOS /目标 - C.(Possible Retain Cycle — iOS/Objective - C)

 我正在解析XML文件中的数据，并相信我已经找到了一个保留周期。 我不知道如何解决它。 简而言之，我正在解析一个块内的一堆浮动，导致我的内存使用量通过屋顶 - 它超过250 MB。 不好。 这是代码： 
 
[TBXML iterateElementsForQuery:@"library_animations" fromElement:rootElement withBlock:^(TBXMLElement *anElement) {
        [self parseLibraryAnimationsElement:anElement];
}];
 
 上面的方法调用以下方法： 
 
- (void)parseLibraryAnimationsElement:(TBXMLElement *)element
{
    [TBXML iterateElementsForQuery:@"animation" fromElement:element withBlock:^(TBXMLElement *anElement) {
        TBXMLElement *extraElement = [TBXML childElementNamed:@"extra" parentElement:anElement];
        TBXMLElement *techniqueElement = [TBXML childElementNamed:@"technique" parentElement:extraElement];

        // grab float data
        **NSData *floatData = [self extractFloatArrayFromElement:techniqueElement];**

        // append data per animation ID
        NSString *key = [NSString stringWithFormat:@"#%@", [TBXML valueOfAttributeNamed:@"id" forElement:anElement]];
        [self.root.sortedAnimationKeys addObject:key];

        // use float data to store color information for this frame
        for (COLLADAMeshGeometry *geometry in self.root.geometries.allValues) {
            AGLKMesh *mesh = geometry.mesh;

            NSMutableData *dynamicColorData = [NSMutableData data];
            GLKVector3 *newColorInfo = (GLKVector3 *)[floatData bytes];

            // cycle through vertices for this mesh and use color float array information
            for (int i = 0; i < mesh.numberOfVertices; i++) {
                AGLKMeshVertex *staticVertex = [mesh vertexAtIndex:i];
                GLKVector3 newColor = newColorInfo[staticVertex->colorIndex];
                GLKVector4 color = GLKVector4Make(newColor.x, newColor.y, newColor.z, 1.0);

                [dynamicColorData appendBytes:&color length:sizeof(color)];
            }

            // get key and store in animation dictionary on the mesh
            [mesh.animationBufferDictionary setObject:dynamicColorData forKey:key];
        }
    }];

    // sort animation keys
    if (self.root.sortedAnimationKeys.count > 0) {
        [self.root.sortedAnimationKeys sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
    }
}
 
 ** ... **之间的方法也在下面。 这是我认为问题所在。 字符串未正确释放。 
 
- (NSData *)extractFloatArrayFromElement:(TBXMLElement *)element
{
    // element is <source>
    NSMutableData *floatData = [NSMutableData data];
    TBXMLElement *floatElement = [TBXML childElementNamed:@"float_array" parentElement:element];
    NSString *stringValues = [TBXML textForElement:floatElement];

    NSArray *values = [stringValues componentsSeparatedByString:@" "];
    for (NSString *value in values) {
        float floatValue = [value floatValue];
        [floatData appendBytes:&floatValue length:sizeof(floatValue)];
    }

    return floatData;
}
 
 我说这是在这里的某个地方，因为当我使用Allocations Instrument时，我会得到大量的CFStrings，如下面的截图所示。 我不确定这是否是足够的信息，但如果有人能看到任何问题，请告诉我。 否则，我可以采取正确方向迈出的一步。 
 
 当我深入查看CFString（不可变）行时，它有许多行，这些行在[NSString componentsSeparatedByString:]中创建。 

I am parsing data from a XML file and believe I've found a retain cycle. I don't have the best understanding how to fix it though. In short, I'm parsing out a bunch of floats within a block which leads to my memory usage going through the roof - it goes over 250 MB. Not good. Here is the code:
 
[TBXML iterateElementsForQuery:@"library_animations" fromElement:rootElement withBlock:^(TBXMLElement *anElement) {
        [self parseLibraryAnimationsElement:anElement];
}];
 
The method above calls the following method:
 
- (void)parseLibraryAnimationsElement:(TBXMLElement *)element
{
    [TBXML iterateElementsForQuery:@"animation" fromElement:element withBlock:^(TBXMLElement *anElement) {
        TBXMLElement *extraElement = [TBXML childElementNamed:@"extra" parentElement:anElement];
        TBXMLElement *techniqueElement = [TBXML childElementNamed:@"technique" parentElement:extraElement];

        // grab float data
        **NSData *floatData = [self extractFloatArrayFromElement:techniqueElement];**

        // append data per animation ID
        NSString *key = [NSString stringWithFormat:@"#%@", [TBXML valueOfAttributeNamed:@"id" forElement:anElement]];
        [self.root.sortedAnimationKeys addObject:key];

        // use float data to store color information for this frame
        for (COLLADAMeshGeometry *geometry in self.root.geometries.allValues) {
            AGLKMesh *mesh = geometry.mesh;

            NSMutableData *dynamicColorData = [NSMutableData data];
            GLKVector3 *newColorInfo = (GLKVector3 *)[floatData bytes];

            // cycle through vertices for this mesh and use color float array information
            for (int i = 0; i < mesh.numberOfVertices; i++) {
                AGLKMeshVertex *staticVertex = [mesh vertexAtIndex:i];
                GLKVector3 newColor = newColorInfo[staticVertex->colorIndex];
                GLKVector4 color = GLKVector4Make(newColor.x, newColor.y, newColor.z, 1.0);

                [dynamicColorData appendBytes:&color length:sizeof(color)];
            }

            // get key and store in animation dictionary on the mesh
            [mesh.animationBufferDictionary setObject:dynamicColorData forKey:key];
        }
    }];

    // sort animation keys
    if (self.root.sortedAnimationKeys.count > 0) {
        [self.root.sortedAnimationKeys sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
    }
}
 
The method between ** ... ** is also below. This is where I believe the issue is. The strings aren't being deallocated properly.
 
- (NSData *)extractFloatArrayFromElement:(TBXMLElement *)element
{
    // element is <source>
    NSMutableData *floatData = [NSMutableData data];
    TBXMLElement *floatElement = [TBXML childElementNamed:@"float_array" parentElement:element];
    NSString *stringValues = [TBXML textForElement:floatElement];

    NSArray *values = [stringValues componentsSeparatedByString:@" "];
    for (NSString *value in values) {
        float floatValue = [value floatValue];
        [floatData appendBytes:&floatValue length:sizeof(floatValue)];
    }

    return floatData;
}
 
I say it's somewhere in here because when I'm using the Allocations Instrument I get a huge number of CFStrings as you can see in the screenshot below. I'm not sure if this is enough information or not, but if someone can see any issues let me know. Otherwise maybe there's a step in the right direction I can take. 
 
When I drill down into the CFString (immutable) line, it has a number of lines that these are created in [NSString componentsSeparatedByString:].

原文：https://stackoverflow.com/questions/19279322