Getting wired issue like main array has been changed if changed value of another array. I think issue is about copying same address, not sure but just thinking of it. I have tried from last 3 hours but unable to get rid from it.
Look at below illustration to get better idea.
List<page> _pageList;
List<page> _orderList = [];
_pageList = _apiResponse.result as List<page>;
_orderList.add(_pageList[0].element);
_orderList[0].title = "XYZ"
//--> Here if I change the `_orderList[0].title` then it also change the `title` inside "_pageList"
How can we prevent the changes in main array?
I got same issue in my one of the project. What I have done is, use json to encode and decode object that help you to make copy of the object so that will not be affected to the main List.
After 3rd line of your code, make changes like below
Elements copyObject = Elements.fromJson(_pageList[0].element.toJson());
// First of all you have to convert your object to the Map and and map to original object like above
_orderList.add(copyObject);
Hope that will help you.
You can use a getter function to create a copy of your list and use that instead of
altering your actual list.
example:
List<Page> get orderList{
return [..._orderList];
}
Lists in Dart store references for complex types, so this is intended behaviour.
From your code:
_orderList.add(_pageList[0].element);
_orderList[0] and _pageList[0].element point to the same reference (if they are non-primitive).
There is no general copy() or clone() method in dart, as far as i know. So you need to copy the object yourself, if you want a separate instance. (see this question)
Related
I'm trying to get the update function in Flame game to work. I have a global variable called newInstructions that's a list that gets updated by a separate function. I want the update function to check when there's a new addition to the list and call a function (populateInfo) with that list as input. After looking at some of the documentation, I've come up with what I think would be the correct code, but it keeps returning this error:
The method 'query' isn't defined by the type 'List'
I think that part of this might come from my not fully understanding what the update/query methods do. With that, what does the query method do and what type should it be? How would I go about changing my code to fix that error?
Here is the update function that I wrote:
#override
void update(double dt){
final instructions = newInstructions.query<List>();
populateInfo(instructions);
}
With that, what does the query method do and what type should it be?
query is a Flame specific method that is used on the OrderedSet in each component where the children are stored, it is used to get children of a specific type. For example to get all Player components:
children.query<Player>();
How would I go about changing my code to fix that error?
Since you want to react to when something is added the newInstructions list you shouldn't do this check in update since this method runs at least 60 times per seconds, it's better to just react once when there is a new instruction added.
This can be done in a few different ways, you could for example put the newInstructions list in a class that you then have an add method on that both adds the instruction to a list contained within the class, and also calls populateInfo. You could also wrap the list in a ChangeNotifier like this.
I just started to use DBx::Class and begun slightly to understand, but it's complex.
I want to call "recursive_update" but I was not able to manage how I can use it.
If I understand the documentation right, I have to include it in the .../My/Schema.pm which was create by DBIx::Class::Schema::Loader?
__PACKAGE__->load_namespaces(default_resultset_class => '+DBIx::Class::ResultSet::RecursiveUpdate');
When I want to update the data I use the ResultSet with the relationships.
my $result = $schema->resultset('Table')->find($id});
$result->recursive_update({
'rel_table' => [....),
});
unfortunately I got an error:
Can't locate object method "recursive_update" via package My::Schema::Result::Table"
Where is my fault?
recursive_update has to be called on a ResultSet object, not a Result object.
You might want to add a helper method to your Result base class (if you already have one else create it, as it makes sense for many things) which gets a ResultSet restricted to the Result object it is called on and calls recursive_update on it.
After realizing that you can't really use UnityEvents in Scriptable Objects (they don't read global variable values correctly). I had to move to another solution for where to store my Dialogs.
The best solution I could find was to just store them in the corresponding NPC-prefab. This is really convenient. However this leaves a bad taste in my mouth, it just feels wrong to store data in a prefab like this. Is it a bad practice?
For example if I were to refactor something in the DialogObject, everything would be lost.
Since I can't seem to successfully store UnityEvents anywhere (can't serialize them as Json and as mentioned Scriptable Objects don't seem to handle them well) I feel like this is the only solution if I want to be able to use the Editor to create Dialogs.
Just checking here first, is this stupid? is there another way?
I am trying to save a List of this:
[System.Serializable]
public class DialogObject {
public List<PageData> conversations = new List<PageData>();
public UnityEvent postEvent; //Invoked on last page of Dialog
}
I would say yes, prefabs are meant to be a template to create new items of a type. You are trying to save data states.
Even though you cannot serialize the UnityEvent, you could serialize its content.
If you assign via inspector, you can use https://docs.unity3d.com/ScriptReference/Events.UnityEventBase.GetPersistentMethodName.html
But then you would not have problem of storage if you know from the start where it goes.
Second solution is when you assign the method to the UnityEvent, store it.
void AddListener (UnityAction ev)
{
MethodInfo mi = ev.Method;
// Use mi
postEvent.AddListener(ev);
}
With the mi reference, you have the name of the method, its type, the object it belongs to and anything you need.
In glade it is possible to set an unique ID to an object. In the code one can obtain a pointer to this object by searching for it's "glade ID" via gtk_builder_get_object().
However for my current use-case I just want to read out this ID from an GObject. What's the API to do so ?
You can't. The builder ID is stored in the builder internally, not in the GObject.
The reason for this is that IDs must be unique per builder, which would be impossible to enforce if you were able to get and set them via some GObject API.
You could use gtk_widget_get_name() to identify an object.
It is possible using Gtk.Buildable.get_name(object). This method will return the Glade object id.
This snippet will print all object ids in your Glade XML:
builder = Gtk.Builder()
builder.add_from_file("my-window.glade"))
for obj in builder.get_objects():
print(Gtk.Buildable.get_name(obj))
As stated by #ptomato it's seems not possible.
I found that in that line in the documentation:
All the fields in the GObject structure are private to the
implementation and should never be accessed directly.
But you can circumvent it because at one point in your code you were refering to it by the id that you typed in (or the code you wrote type in) so you just need to store it at that point. And link it somehow (with a variable or a data structure) to the name of the variable holding the object.
Hi I have a situation where I need to look up the number of recently viewed products on catalog/product/view.phtml. In the recently viewed 'product_viewed.phtml' file it calls
$_products = $this->getRecentlyViewedProducts()
to get the recently viewed. How would I access this method from within the catalog/product/view.phtml file?
I don't know where this method is. I've tried searching for it but it doesn't seem to exist. When I write click it in Netbeans and click go to declaration it takes me to
class Mage_Reports_Block_Product_Viewed extends Mage_Reports_Block_Product_Abstract
Actually on the class itself. This class only has _toHtml(), getCount(), and getPageSize() methods.
I just need to know whether there are any recently viewed products.
Any help most appreciated!
Billy
If you look into 'Mage_Reports_Block_Product_Viewed', you will notice:
$this->setRecentlyViewedProducts($this->getItemsCollection());
That 'getItemsCollection' method is defined in the abstract class... And you will notice this abstract class will create a model based on $_indexName defined in the (subclassed) block.
If you just want the collection, you can probably get away with:
$_products = Mage::getModel('reports/product_index_viewed')->getCollection();
And then adding whatever you want to the collection:
$_products
->addAttributeToSelect('*')
->setAddedAtOrder();
// optionally add other methods similar to Mage_Reports_Block_Product_Abstract::getItemsCollection
Another approach that might be more suited would be to create the original block:
$productViewedBlock = $this->getLayout()->createBlock('reports/product_viewed');
On which you can simply call whatever you want:
$_collection = $productViewedBlock->getItemsCollection();
$_count = $productViewedBlock->getCount();
The getRecentlyViewedProducts function is a magical getter that gets the data that was set with setRecentlyViewedProducts in app/code/core/Mage/Reports/Block/Product/Viewed.php (which builds it using app/code/core/Mage/Reports/Block/Product/Abstract.php's function _getRecentProductsCollection).
This is complicated stuff that you don't want to reproduce; its better, IMO to make your own Block that extends Mage_Catalog_Block_Product_Abstract that will give you access to the same functionality, and drop your new block into the page you're working on.