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  • Why do case class companion objects extend FunctionN?

    - by retronym
    When you create a case class, the compiler creates a corresponding companion object with a few of the case class goodies: an apply factory method matching the primary constructor, equals, hashCode, and copy. Somewhat oddly, this generated object extends FunctionN. scala> case class A(a: Int) defined class A scala> A: (Int => A) res0: (Int) => A = <function1> This is only the case if: There is no manually defined companion object There is exactly one parameter list There are no type arguments The case class isn't abstract. Seems like this was added about two years ago. The latest incarnation is here. Does anyone use this, or know why it was added? It increases the size of the generated bytecode a little with static forwarder methods, and shows up in the #toString() method of the companion objects: scala> case class A() defined class A scala> A.toString res12: java.lang.String = <function0>

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  • How do I use a variable within an extended class public variable

    - by Gerry Humphrey
    Have a class that I am using, I am overriding variables in the class to change them to what values I need, but I also not sure if or how to handle an issue. I need to add a key that is generated to each of this URLs before the class calls them. I cannot modify the class file itself. use Theme/Ride class ETicket extends Ride { public $key='US20120303'; // Not in original class public $accessURL1 = 'http://domain.com/keycheck.php?key='.$key; public $accessURL2 = 'http://domain.com/keycheck.php?key='.$key; } I understand that you cannot use a variable in the setting of the public class variables. Just not sure what would be the way to actually do something like this in the proper format. My OOP skills are weak. I admit it. So if someone has a suggestion on where I could read up on it and get a clue, it would be appreciated as well. I guess I need OOP for Dummies. =/

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  • Nested Class member function can't access function of enclosing class. Why?

    - by Rahul
    Please see the example code below: class A { private: class B { public: foobar(); }; public: foo(); bar(); }; Within class A & B implementation: A::foo() { //do something } A::bar() { //some code foo(); //more code } A::B::foobar() { //some code foo(); //<<compiler doesn't like this } The compiler flags the call to foo() within the method foobar(). Earlier, I had foo() as private member function of class A but changed to public assuming that B's function can't see it. Of course, it didn't help. I am trying to re-use the functionality provided by A's method. Why doesn't the compiler allow this function call? As I see it, they are part of same enclosing class (A). I thought the accessibility issue for nested class meebers for enclosing class in C++ standards was resolved. How can I achieve what I am trying to do without re-writing the same method (foo()) for B, which keeping B nested within A? I am using VC++ compiler ver-9 (Visual Studio 2008). Thank you for your help.

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  • Drawbacks with using Class Methods in Objective C.

    - by RickiG
    Hi I was wondering if there are any memory/performance drawbacks, or just drawbacks in general, with using Class Methods like: + (void)myClassMethod:(NSString *)param { // much to be done... } or + (NSArray*)myClassMethod:(NSString *)param { // much to be done... return [NSArray autorelease]; } It is convenient placing a lot of functionality in Class Methods, especially in an environment where I have to deal with memory management(iPhone), but there is usually a catch when something is convenient? An example could be a thought up Web Service that consisted of a lot of classes with very simple functionality. i.e. TomorrowsXMLResults; TodaysXMLResults; YesterdaysXMLResults; MondaysXMLResults; TuesdaysXMLResults; . . . n I collect a ton of these in my Web Service Class and just instantiate the web service class and let methods on this class call Class Methods on the 'Results' Classes. The classes are simple but they handle large amount of Xml, instantiate lots of objects etc. I guess I am asking if Class Methods lives or are treated different on the stack and in memory than messages to instantiated objects? Or are they just instantiated and pulled down again behind the scenes and thus, just a way of saving a few lines of code?

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  • Abstract base class puzzle

    - by 0x80
    In my class design I ran into the following problem: class MyData { int foo; }; class AbstraktA { public: virtual void A() = 0; }; class AbstraktB : public AbstraktA { public: virtual void B() = 0; }; template<class T> class ImplA : public AbstraktA { public: void A(){ cout << "ImplA A()"; } }; class ImplB : public ImplA<MyData>, public AbstraktB { public: void B(){ cout << "ImplB B()"; } }; void TestAbstrakt() { AbstraktB *b = (AbstraktB *) new ImplB; b->A(); b->B(); }; The problem with the code above is that the compiler will complain that AbstraktA::A() is not defined. Interface A is shared by multiple objects. But the implementation of A is dependent on the template argument. Interface B is the seen by the outside world, and needs to be abstrakt. The reason I would like this is that it would allow me to define object C like this: Define the interface C inheriting from abstrakt A. Define the implementation of C using a different datatype for template A. I hope I'm clear. Is there any way to do this, or do I need to rethink my design?

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  • Function pointers to member functions

    - by Jacob
    There are several duplicates of this but nobody explains why I can use a member variable to store the pointer (in FOO) but when I try it with a local variable (in the commented portion of BAR), it's illegal. Could anybody explain this? #include <iostream> using namespace std; class FOO { public: int (FOO::*fptr)(int a, int b); int add_stuff(int a, int b) { return a+b; } void call_adder(int a, int b) { fptr = &FOO::add_stuff; cout<<(this->*fptr)(a,b)<<endl; } }; class BAR { public: int add_stuff(int a, int b) { return a+b; } void call_adder(int a, int b) { //int (BAR::*fptr)(int a, int b); //fptr = &BAR::add_stuff; //cout<<(*fptr)(a,b)<<endl; } }; int main() { FOO test; test.call_adder(10,20); return 0; }

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  • How do I call +class methods in Objective C without referencing the class?

    - by TimM
    I have a series of "policy" objects which I thought would be convenient to implement as class methods on a set of policy classes. I have specified a protocol for this, and created classes to conform to (just one shown below) @protocol Counter +(NSInteger) countFor: (Model *)model; @end @interface CurrentListCounter : NSObject <Counter> +(NSInteger) countFor: (Model *)model; @end I then have an array of the classes that conform to this protocol (like CurrentListCounter does) +(NSArray *) availableCounters { return [[[NSArray alloc] initWithObjects: [CurrentListCounter class],[AllListsCounter class], nil] autorelease]; } Notice how I am using the classes like objects (and this might be my problem - in Smalltalk classes are objects like everything else - I'm not sure if they are in Objective-C?) My exact problem is when I want to call the method when I take one of the policy objects out of the array: id<Counter> counter = [[MyModel availableCounters] objectAtIndex: self.index]; return [counter countFor: self]; I get a warning on the return statement - it says -countFor: not found in protocol (so its assuming its an instance method where I want to call a class method). However as the objects in my array are instances of class, they are now like instance methods (or conceptually they should be). Is there a magic way to call class methods? Or is this just a bad idea and I should just create instances of my policy objects (and not use class methods)?

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  • Unable to Get values from Web Form to a PHP Class to Display

    - by kentrenholm
    I am having troubles getting the value from my variables submitted via a web form using a PHP class file. Here is my structure of the web page: Order Form Page Process.php Page Book.php Page I can easily get the user data entered (on Order Form Page), process, and display it on the Process.php page. The issue is that I must create a Book class and print the details of the data using the Book class. I have an empty constructor printing out "created" so I know my constructor is being called. I also am able to print the word "title" so I know I can print to the screen by using the Book class. My issue is that I can't get values in my variables in the Book class. Here is my variable declaration: private $title; Here is my printDetails function: public function printDetails () { echo "Title: " . $this->title . "<br />"; } Here is my new instance of the book class: $bookNow = new book; Here are my get and set functions: function __getTitle($title) { return $this->$title; } function __setTitle($title,$value) { $this->$title = $value; } I do have four other variables that I'm looking to display as well. Each of those have their own variable declaration, a line in printDetails, and their own setter and getter. Lastly, I also have a call to the Book class in my process PHP. It looks like this: function __autoload($book) { include $book . '.php'; } $bookNow = new book(); Any help, much appreciated. It must be something so very small (I'm hoping).

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  • Using Aggregate functions in DataView filters

    - by Shrewd Demon
    hi, i have a DataTable that has a column ("Profit"). What i want is to get the Sum of all the values in this table. I tried to do this in the following manner... DataTable dsTemp = new DataTable(); dsTemp.Columns.Add("Profit"); DataRow dr = null; dr = dsTemp.NewRow(); dr["Profit"] = 100; dsTemp.Rows.Add(dr); dr = dsTemp.NewRow(); dr["Profit"] = 200; dsTemp.Rows.Add(dr); DataView dvTotal = dsTemp.DefaultView; dvTotal.RowFilter = " SUM ( Profit ) "; DataTable dt = dvTotal.ToTable(); But i get an error while applying the filter... how can i get the Sum of the Profit column in a variable thank you...

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  • Exclude first child with XSL-T

    - by zneak
    Hello, What I'm trying to do is fairly simple, but I can't find the way to. I just want to iterate over the children of a node excluding the first child. For instance, in this XML snippet, I would want all the <bar> elements, except the first one: <foo> <Bar>Example</Bar> <Bar>This is an example</Bar> <Bar>Another example</Bar> <Bar>Bar</Bar> </foo> There is no common attribute by which I can filter (like an id tag or something similar). Any suggestions?

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  • replace selfjoin with analytic functions

    - by edwards
    Hi Any ideas how i go about replacing the following self join using analytics SELECT t1.col1 col1, t1.col2 col2, SUM((extract(hour FROM (t1.times_stamp - t2.times_stamp)) * 3600 + extract(minute FROM ( t1.times_stamp - t2.times_stamp)) * 60 + extract(second FROM ( t1.times_stamp - t2.times_stamp)) ) ) div, COUNT(*) tot_count FROM tab1 t1, tab1 t2 WHERE t2.col1 = t1.col1 AND t2.col2 = t1.col2 AND t2.col3 = t1.sequence_num AND t2.times_stamp < t1.times_stamp AND t2.col4 = 3 AND t1.col4 = 4 AND t2.col5 NOT IN(103,123) AND t1.col5 != 549 GROUP BY t1.col1, t1.col2

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  • Abstract class reference

    - by AlgoMan
    Can i have a class Class Room{ ~Room(); virtual cost() =0; } Class Hotel{ map rooms; /* */ }; will my hotel become abstract ? Can it hold the list of concrete Room objects that are derived from Room ?

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  • How to combine these two JavaScript functions?

    - by user289346
    var curtext = "View large image"; function changeSrc() { if (curtext == "View large image") { document.getElementById("boldStuff").innerHTML = "View small image"; curtext="View small image"; } else { document.getElementById("boldStuff").innerHTML = "View large image"; curtext = "View large image"; } } var curimage = "cottage_small.jpg"; function changeSrc() { if (curimage == "cottage_small.jpg") { document.getElementById("myImage").src = "cottage_large.jpg"; curimage = "cottage_large.jpg"; } else { document.getElementById("myImage").src = "cottage_small.jpg"; curimage = "cottage_small.jpg"; } } </script> </head> <body> <!-- Your page here --> <h1> Pink Knoll Properties</h1> <h2> Single Family Homes</h2> <p> Cottage:<strong>$149,000</strong><br/> 2 bed, 1 bath, 1,189 square feet, 1.11 acres <br/><br/> <a href="#" onclick="changeSrc()"><b id="boldStuff" />View large image</a></p> <p><img id="myImage" src="cottage_small.jpg" alt="Photo of a cottage" /></p> </body> I need help, how to put as one function with two arguments? That means when you click, the image and text both will be change. Thank you! Bianca

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  • Passing variables to functions

    - by Faken
    A quick question: When i pass a variable to a function, dose the program make a copy of that variable to use in the function? If it dose and I knew that the function would only read the variable and never write to it, is it possible to pass a variable to the function without creating a copy of that variable or should I just leave that up to the compiler optimizations to do that automatically for me?

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  • Variadic functions and arguments assignment in C/C++

    - by Rizo
    I was wondering if in C/C++ language it is possible to pass arguments to function in key-value form. For example in python you can do: def some_function(arg0 = "default_value", arg1): # (...) value1 = "passed_value" some_function(arg1 = value1) So the alternative code in C could look like this: void some_function(char *arg0 = "default_value", char *arg1) { ; } int main() { char *value1 = "passed_value"; some_function(arg1 = value1); return(0); } So the arguments to use in some_function would be: arg0 = "default_value" arg1 = "passed_value" Any ideas?

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  • Stored Functions with Linq to Entities

    - by Lawnmower
    Hi, How can I make a MS-SQL stored function availabe in LINQ expressions if using the Entity framework? The SQL function was created with CREATE FUNCTION MyFunction(@name) ...). I was hoping to access it similarly to this: var data = from c in entities.Users where MyFunction(c.name) = 3; Unfortunately I have only .NET 3.5 available.

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  • Entity Framework 4.1 (Code First) audit column

    - by Ken Pespisa
    I'm using Entity Framework 4.1 with a Code-First approach on an ASP.NET MVC site Say I have an entity named Profile that keeps track of a user's favorite book, and I want to track when the user updates their favorite book. UPDATED: Using the class below as an example, I want to set the FavoriteBookLastUpdated property to the current date whenever the value of the FavoriteBook property changes. public class Profile { public int Id { get; set; } public string Name { get; set; } public string FavoriteBook { get; set; } public DateTime? FavoriteBookLastUpdated { get; set; } } Right now I just update that field, if appropriate, in the controller's Edit action before calling the DBContext's SaveChanges() method. Is there a way I can put that logic in my model somehow? I'd prefer not to use triggers on the database side.

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  • How do implement a breadth first traversal?

    - by not looking for answer
    //This is what I have. I thought pre-order was the same and mixed it up with depth first! import java.util.LinkedList; import java.util.Queue; public class Exercise25_1 { public static void main(String[] args) { BinaryTree tree = new BinaryTree(new Integer[] {10, 5, 15, 12, 4, 8 }); System.out.print("\nInorder: "); tree.inorder(); System.out.print("\nPreorder: "); tree.preorder(); System.out.print("\nPostorder: "); tree.postorder(); //call the breadth method to test it System.out.print("\nBreadthFirst:"); tree.breadth(); } } class BinaryTree { private TreeNode root; /** Create a default binary tree */ public BinaryTree() { } /** Create a binary tree from an array of objects */ public BinaryTree(Object[] objects) { for (int i = 0; i < objects.length; i++) { insert(objects[i]); } } /** Search element o in this binary tree */ public boolean search(Object o) { return search(o, root); } public boolean search(Object o, TreeNode root) { if (root == null) { return false; } if (root.element.equals(o)) { return true; } else { return search(o, root.left) || search(o, root.right); } } /** Return the number of nodes in this binary tree */ public int size() { return size(root); } public int size(TreeNode root) { if (root == null) { return 0; } else { return 1 + size(root.left) + size(root.right); } } /** Return the depth of this binary tree. Depth is the * number of the nodes in the longest path of the tree */ public int depth() { return depth(root); } public int depth(TreeNode root) { if (root == null) { return 0; } else { return 1 + Math.max(depth(root.left), depth(root.right)); } } /** Insert element o into the binary tree * Return true if the element is inserted successfully */ public boolean insert(Object o) { if (root == null) { root = new TreeNode(o); // Create a new root } else { // Locate the parent node TreeNode parent = null; TreeNode current = root; while (current != null) { if (((Comparable)o).compareTo(current.element) < 0) { parent = current; current = current.left; } else if (((Comparable)o).compareTo(current.element) > 0) { parent = current; current = current.right; } else { return false; // Duplicate node not inserted } } // Create the new node and attach it to the parent node if (((Comparable)o).compareTo(parent.element) < 0) { parent.left = new TreeNode(o); } else { parent.right = new TreeNode(o); } } return true; // Element inserted } public void breadth() { breadth(root); } // Implement this method to produce a breadth first // search traversal public void breadth(TreeNode root){ if (root == null) return; System.out.print(root.element + " "); breadth(root.left); breadth(root.right); } /** Inorder traversal */ public void inorder() { inorder(root); } /** Inorder traversal from a subtree */ private void inorder(TreeNode root) { if (root == null) { return; } inorder(root.left); System.out.print(root.element + " "); inorder(root.right); } /** Postorder traversal */ public void postorder() { postorder(root); } /** Postorder traversal from a subtree */ private void postorder(TreeNode root) { if (root == null) { return; } postorder(root.left); postorder(root.right); System.out.print(root.element + " "); } /** Preorder traversal */ public void preorder() { preorder(root); } /** Preorder traversal from a subtree */ private void preorder(TreeNode root) { if (root == null) { return; } System.out.print(root.element + " "); preorder(root.left); preorder(root.right); } /** Inner class tree node */ private class TreeNode { Object element; TreeNode left; TreeNode right; public TreeNode(Object o) { element = o; } } }

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  • Data not displayed first time in android after copying the file from assets to data folder

    - by Thinkcomplete
    Description I have used the code tip from http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/ to copy a pre-filled data file to the target and handled this in a asynch task Problem : On starting the application it gives error and shuts down first time, starting again without any change it works perfectly fine. So first time after the file is copied, the error comes but after that no issues. Please help Code attached:.. private class CopyDatabase extends AsyncTask<String, Void, Boolean> { private final ProgressDialog dialog = new ProgressDialog(BabyNames.this); protected void onPreExecute() { this.dialog.setMessage("Loading..."); this.dialog.show(); } @Override protected Boolean doInBackground(String... params) { // TODO Auto-generated method stub try { namesDBSQLHelper.createDatabase(); return null; } catch(IOException ioe){ ioe.printStackTrace(); } return null; } protected void onPostExecute(final Boolean success){ if (this.dialog.isShowing()){ this.dialog.dismiss(); } } }

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  • Calling and writing jquery/javascript functions

    - by Ankur
    I think I have not got the syntax correct for writing a javascript function and calling it to assign its return value to a variable. My function is: getObjName(objId){ var objName =""; $.ajax( { type : "GET", url : "Object", dataType: 'json', data : "objId="+objId, success : function(data) { objName = data; } }); return objName; } I am trying to call it and assign it to a variable with: var objName = getObjName(objId); However Eclipse is telling me that "the function getObjName(any) is undefined"

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  • Question of using static_cast on "this" pointer in a derived object to base class

    - by Johnyy
    Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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  • Save VM properties with EF code first

    - by Julien
    I thought this would be simple but can't find any good examples. public Class BookVm : ImplementsPropertyChanged { public int BookId {get;set;} private bool _favorite; public bool Favorite { get { return _favorite; } set { _favorite = value; OnPropertyChanged("Favorite"); MyDbContext.SaveChanges() // this does not work } } Then in my XAML bound to Book <CheckBox Content="Favorite" IsChecked="{Binding Favorite}" /> How and when do I call SaveChanges() on my DatabaseContext? I don't want to implement a save button. If I intercept the PropertyChange event and call SaveChanges, nothing seems to happen. My object is modified in memory but the database does not see a change. My BookVm class is created on application startup like so: foreach (var book in MyDbContext.Books) Books.Add(book); Where Books is an ObservableCollection<Book> in my MainWindowVm

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  • as3 custom functions

    - by pixeltocode
    hi, i'm new to AS3. how do i go about executing a custom function n number of times and then executing another function n number of times repeatedly? eg. function firstOne():void { } function secondOne():void { } i need firstOne() executed say 3 times and then secondOne() 3 times and then firstOne 3 times again and so on. thanks

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  • How do you overide a class that is called by another class with parent::method

    - by dan.codes
    I am trying to extend Mage_Catalog_Block_Product_View I have it setup in my local directory as its own module and everything works fine, I wasn't getting the results that I wanted. I then saw that another class extended that class as well. The method I am trying to override is the protected function _prepareLayout() This is the function class Mage_Review_Block_Product_View extends Mage_Catalog_Block_Product_View protected function _prepareLayout() { $this-&gt;getLayout()-&gt;createBlock('catalog/breadcrumbs'); $headBlock = $this-&gt;getLayout()-&gt;getBlock('head'); if ($headBlock) { $title = $this-&gt;getProduct()-&gt;getMetaTitle(); if ($title) { $headBlock-&gt;setTitle($title); } $keyword = $this-&gt;getProduct()-&gt;getMetaKeyword(); $currentCategory = Mage::registry('current_category'); if ($keyword) { $headBlock-&gt;setKeywords($keyword); } elseif($currentCategory) { $headBlock-&gt;setKeywords($this-&gt;getProduct()-&gt;getName()); } $description = $this-&gt;getProduct()-&gt;getMetaDescription(); if ($description) { $headBlock-&gt;setDescription( ($description) ); } else { $headBlock-&gt;setDescription( $this-&gt;getProduct()-&gt;getDescription() ); } } return parent::_prepareLayout(); } I am trying to modify it just a bit with the following, keep in mind I know there is a title prefix and suffix but I needed it only for the product page and also I needed to add text to the description. class MyCompany_Catalog_Block_Product_View extends Mage_Catalog_Block_Product_View protected function _prepareLayout() { $storeId = Mage::app()-&gt;getStore()-&gt;getId(); $this-&gt;getLayout()-&gt;createBlock('catalog/breadcrumbs'); $headBlock = $this-&gt;getLayout()-&gt;getBlock('head'); if ($headBlock) { $title = $this-&gt;getProduct()-&gt;getMetaTitle(); if ($title) { if($storeId == 2){ $title = "Pool Supplies Fast - " .$title; $headBlock-&gt;setTitle($title); } $headBlock-&gt;setTitle($title); }else{ $path = Mage::helper('catalog')-&gt;getBreadcrumbPath(); foreach ($path as $name =&gt; $breadcrumb) { $title[] = $breadcrumb['label']; } $newTitle = "Pool Supplies Fast - " . join($this-&gt;getTitleSeparator(), array_reverse($title)); $headBlock-&gt;setTitle($newTitle); } $keyword = $this-&gt;getProduct()-&gt;getMetaKeyword(); $currentCategory = Mage::registry('current_category'); if ($keyword) { $headBlock-&gt;setKeywords($keyword); } elseif($currentCategory) { $headBlock-&gt;setKeywords($this-&gt;getProduct()-&gt;getName()); } $description = $this-&gt;getProduct()-&gt;getMetaDescription(); if ($description) { if($storeId == 2){ $description = "Pool Supplies Fast - ". $this-&gt;getProduct()-&gt;getName() . " - " . $description; $headBlock-&gt;setDescription( ($description) ); }else{ $headBlock-&gt;setDescription( ($description) ); } } else { if($storeId == 2){ $description = "Pool Supplies Fast: ". $this-&gt;getProduct()-&gt;getName() . " - " . $this-&gt;getProduct()-&gt;getDescription(); $headBlock-&gt;setDescription( ($description) ); }else{ $headBlock-&gt;setDescription( $this-&gt;getProduct()-&gt;getDescription() ); } } } return Mage_Catalog_Block_Product_Abstract::_prepareLayout(); } This executs fine but then I notice that the following class Mage_Review_Block_Product_View_List extends which extends Mage_Review_Block_Product_View and that extends Mage_Catalog_Block_Product_View as well. Inside this class they call the _prepareLayout as well and call the parent with parent::_prepareLayout() class Mage_Review_Block_Product_View_List extends Mage_Review_Block_Product_View protected function _prepareLayout() { parent::_prepareLayout(); if ($toolbar = $this-&gt;getLayout()-&gt;getBlock('product_review_list.toolbar')) { $toolbar-&gt;setCollection($this-&gt;getReviewsCollection()); $this-&gt;setChild('toolbar', $toolbar); } return $this; } So obviously this just calls the same class I am extending and runs the function I am overiding but it doesn't get to my class because it is not in my class hierarchy and since it gets called after my class all the stuff in the parent class override what I have set. I'm not sure about the best way to extend this type of class and method, there has to be a good way to do this, I keep finding I am running into issues when trying to overide these prepare methods that are derived from the abstract classes, there seems to be so many classes overriding them and calling parent::method. What is the best way to override these functions?

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