I'm using EaselJS for a project, and have the need to store the details of various 'Shape' objects in a database, so that they can be re-drawn at another time.
My project has the 'Stage' set up so that I can drag-draw a box, which is saved into the database when completed. I intend to make it usable for drawing polygons also.
My database has a table in it called 'polyshapes', which stores the Shape.id, Shape.name, Shape.x, Shape.y, Shape.rotation. It also has a field called 'graphics' where I can store some sort of text string representing the Shape.graphics object.
When I draw a box, I'm able to store a string of the 'graphics' using: JSON.stringify(Myshape.graphics).
When I load this shape from the database, I create a new createjs.Shape() object, and then use Myshape.graphics = JSON.parse(graphicsString) to load the graphics.
Unfortunately this doesn't seem to work, as it doesn't load the required functions within the object.
I have also tried just individually updating some specific graphics attributes such as 'command', '_instructions', '_stroke', '_strokeStyle'. But I still can get the required graphic to re-draw.
Ideally, I'd only need to store the 'instructions' attribute of the Shape.graphics when I drag-draw it, and then when loading from the DB, I would just use a method to re-create those graphics when provided with the 'instructions' data. However I can't seem to see a suitable method for doing this.
I have also looked into the decodePath() graphics method. This would be useful, except that there doesn't appear to be an inverse method 'encodePath()' to allow me to serialize it in the first place.
How can I store the Shape.graphics data in a database, and then recall it later to rebuild a new Shape() object?
Thanks,
Hugh.
Related
I'm calling:
- (void)updateWithValues:(NSDictionary *)values
version:(uint64_t)version
in an NSIncrementalStore subclass in order to update the cache with update NSManagedObject values. My question concerns the values argument. Do I only need to put in the updated attributes or a complete new copy of the data?
The description in the documentation says: "Update the values and version to reflect new data being saved to or loaded from the external store. // The values dictionary is in the same format as the initializer."
It isn't clear to me whether or not the "values" that "reflect the new data" refers to only the updated attributes or all the attributes in the object.
It requires the complete data. I agree it wasn't very clear but I suppose the reason is so you can do the conflict handling first. The annoying thing is there is no way to get the values back from the node to merge in the new ones and set them again. Annoyingly this means you can't use the node as your cache object, I'm still learning the NSIncrementalStore so likely there reason for this design will come clear at some point.
I have a Android java project with quite complex datatypes including ArrayLists of other complex datatypes. I’m trying to store my data in a database using ORMLite (4.42).
I have major problems converting between ArrayLists and ForeignCollection, has anyone manage to do this?
I don’t want a continuous sync with the database, instead I have a save method that saves the entire structure and a read method that restores the entire method. After an object is restored from the database, the object is sent via interfaces where the receiver expects a ArrayLists and not orm lite ForeignCollections.
My approach is the following. For each ArrayList I have a complementary ForeignCollection. Before storing an object to the database, the content of the ArrayList is copied to the ForeignCollection, and when read back, vice versa.
When I read out a data structure from the database, I want the ensure that the entire structure is restored since later on, the object will be sent to users that are not aware about orm lite package, thus I set eager = true.
My complex datatype looks like this:
#DatabaseTable(tableName = "accounts")
public class Account {
#DatabaseField(generatedId = true)
private int id;
#ForeignCollectionField (eager = true, maxEagerLevel = 2)
private ForeignCollection<Order> ordersFoC;
private ArrayList<Order> ordersArL;
The Problem
Before storing the Account to the database, I tried to do the following. My hope was to copy the objects in the ArrayList to the ForeignCollection and the update the database with the Account object. The object myAccount has the same id as an object in the database so I expect an update of that object.
ordersFoC.addAll(orderArL);
myDao.createOrUpdate(myAccount);
No luck. The addAll method does directly write the orders to the database so I end up with duplicates of all orders since “addAll” adds and does not update any existing records.
So I tried to first remove all the orders from the database, but again with no luck:
ordersFoC.clear(); // Also tried: ordersFoC.removeAll(ordersFoC);
ordersFoC.addAll(orderArL);
myDao.createOrUpdate(myAccount);
The objects are not removed from the database. I read at groups.google.com (by Philip Fu) that this is a “known” problem with ormlite, that eager ForeignCollection does not play well with removeAll() or clear().
Is there a pattern that I have missed that allows me to work with objects that includes ArrayLists of complex types using the ormlite framework?
I've got my code working with ArrayLists ok. I declared my fields like this:
#ForeignCollectionField(eager = true, maxEagerForeignCollectionLevel = 99)
private Collection<PersonalNameStructure> personalnamestructures = new ArrayList<>();
and the getter as
public List<PersonalNameStructure> getPersonalNameStructures() {
return new ArrayList<>(personalnamestructures) ;
}
so it creates the ArrayList on the fly rather than trying to maintain it.
Obviously you may realise this already, but you also need to be careful around writing the objects as the eager setting affects reading foreign collections, it doesn't do anything for foreign fields or when writing a record.
The usual use for a combo box is to let it display options to the user, and then you get an OBJECT out of it. In Win32, you do it by using the CB_SETITEMDATA and CB_GETITEMDATA messages, casting between int and object pointers. In XAML, you set up a data template and the item in the list IS the object.
What is the Correct way to get this effect with a GtkComboBox?
GtkComboBox normally uses a GtkListStore as the underlaying model.
You need to create one with an extra column for the object you want to store and as you insert new items in the combo's model you also need to provide the object you want to associate with that row/item.
I am using a TreeView with a ListStore as model. When the user clicks on a row I want to take some action but not using the values in the cells, but using the data I created the row from...
Currently I have the TreeView, the TreeModel (ListStore) and my own data (which I ironically call model)..
So the Questions are:
Is it "right" to have a model - an object representation of the data I want to display and fill a ListStore with that data to display in a TreeView, or would it be better to implement an own version of TreeModel (wrapping my data-model) to display the data?
And also:
If someone double-clicks in a row I can get the RowActivated event (using C#/Gtk#) which provides a Path to the activated row. With that I can get a TreeIter and using that I can get the value of a cell. But what is the best practice to find the data object from which the row was constructed in the first place?\
(Somehow this question got me to the first one - by thinking would getting the data object more easy if I tried to implement my own TreeModel...)
It's quite awkward/difficult to implement TreeModel, so most people simply synch the data from their "real" model into a TreeStore or ListStore.
The columns in the store do not have to match the columns in the view in any way. For example, you can have a column that contains your real managed data objects.
When you add a cellrenderer to a TreeView (visual) column, you can add mappings between its properties and the columns of the store. For example, you could map one store column to the font of a text cellrenderer, and another store column to the text property of the same cellrenderer. Each time the cellrenderer is used to render a particular cell, the mappings will be used to retrieve the values from the store and apply them to the properties of the renderer before it renders.
Here's an example of a mapping:
treeView.AppendColumn ("Title", renderer, "text", 0, "editable", 4);
This maps store column 0 to the renderer's text GTK property and maps store column 4 to the editable property. For GTK property names you can check the GTK docs. Note that the example above uses a convenience method that adds a column, adds a renderer to it and add an arbitrary number of mapping via params. To add mappings directly to a column, for example a column with multiple renderers, pack the renderers into the column then use TreeViewColumn.AddAttribute or TreeViewColumn.SetAttributes.
You can also set up a custom data function that will be used instead of mappings. This allows you to set the properties of the renderer directly, given a TreeIter and the store - so, if all the data you want to display is trivially derived from your real data objects, you could even have your store only contain a single column of these objects, and use data funcs for all the view columns.
Here's an example of a data func that does exactly what the mapping example above does:
treeColumn.SetCellDataFunc (renderer, delegate (TreeViewColumn col,
CellRenderer cell, TreeModel model, TreeIter iter)
{
var textCell = (CellRendererText) cell;
textCell.Text = (string) model.GetValue (iter, 0);
textCell.Editable = (bool) model.GetValue (iter, 4);
});
Obviously data functions are much more powerful because they enable you not only to use properties of more complex GTK objects, but also to implement more complex display logic - for example, lazily processing derived values only when the cell is actually rendered.
How can I go about storing a vb.net user defined object in a sql database. I am not trying to replicate the properties with columns. I mean something along the lines of converting or encoding my object to a byte array and then storing that in a field in the db. Like when you store an instance of an object in session, but I need the info to persist past the current session.
#Orion Edwards
It's not a matter of stances. It's because one day, you will change your code. Then you will try de-serialize the old object, and YOUR PROGRAM WILL CRASH.
My Program will not "CRASH", it will throw an exception. Lucky for me .net has a whole set of classes dedicated for such an occasion. At which time I will refresh my stale data and put it back in the db. That is the point of this one field (or stance, as the case may be).
You can use serialization - it allows you to store your object at least in 3 forms: binary (suitable for BLOBs), XML (take advantage of MSSQL's XML data type) or just plain text (store in varchar or text column)
Before you head down this road towards your own eventual insanity, you should take a look at this (or one day repeat it):
http://thedailywtf.com/Articles/The-Mythical-Business-Layer.aspx
Persisting objects in a database is not a good idea. It kills all the good things that a database is designed to do.
You could use the BinaryFormatter class to serialize your object to a binary format, then save the resulting string in your database.
The XmlSerializer or the DataContractSerializer in .net 3.x will do the job for you.
#aku, lomaxx and bdukes - your solutions are what I was looking for.
#1800 INFORMATION - while i appreciate your stance on the matter, this is a special case of data that I get from a webservice that gets refreshed only about once a month. I dont need the data persisted in db form because thats what the webservice is for. Below is the code I finally got to work.
Serialize
#'res is my object to serialize
Dim xml_serializer As System.Xml.Serialization.XmlSerializer
Dim string_writer As New System.IO.StringWriter()
xml_serializer = New System.Xml.Serialization.XmlSerializer(res.GetType)
xml_serializer.Serialize(string_writer, res)
Deserialize
#'string_writer and xml_serializer from above
Dim serialization As String = string_writer.ToString
Dim string_reader As System.IO.StringReader
string_reader = New System.IO.StringReader(serialization)
Dim res2 As testsedie.EligibilityResponse
res2 = xml_serializer.Deserialize(string_reader)
What you want to do is called "Serializing" your object, and .Net has a few different ways to go about it. One is the XmlSerializer class in the System.Xml.Serialization namespace.
Another is in the System.Runtime.Serialization namespace. This has support for a SOAP formatter, a binary formatter, and a base class you can inherit from that all implement a common interface.
For what you are talking about, the BinaryFormatter suggested earlier will probably have the best performance.
I'm backing #1800 Information on this one.
Serializing objects for long-term storage is never a good idea
while i appreciate your stance on the matter, this is a special case of data that I get from a webservice that gets refreshed only about once a month.
It's not a matter of stances. It's because one day, you will change your code. Then you will try de-serialize the old object, and YOUR PROGRAM WILL CRASH.
If it crashes (or throws an exception) all you are left with is a bunch of binary data to try and sift through to recreate your objects.
If you are only persisting binary why not just save straight to disk. You also might want to look at using something like xml as, as has been mentioned, if you alter your object definition you may not be able to unserialise it without some hard work.