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• Python Glade could not create GladeXML Object

  - by Peter

  Hey, I've created a simple window GUI in Glade 3.6.7 and I am trying to import it into Python. Every time I try to do so I get the following error: (queryrelevanceevaluation.py:8804): libglade-WARNING **: Expected <glade-interface>. Got <interface>. (queryrelevanceevaluation.py:8804): libglade-WARNING **: did not finish in PARSER_FINISH state Traceback (most recent call last): File "queryrelevanceevaluation.py", line 17, in <module> app = QueryRelevanceEvaluationApp() File "queryrelevanceevaluation.py", line 10, in __init__ self.widgets = gtk.glade.XML(gladefile) RuntimeError: could not create GladeXML object My Python Code: #!/usr/bin/env python import gtk import gtk.glade class QueryRelevanceEvaluationApp: def __init__(self): gladefile = "foo.glade" self.widgets = gtk.glade.XML(gladefile) dic = {"on_buttonGenerate_clicked" : self.on_buttonGenerate_clicked} self.widgets.signal_autoconnect(dic) def on_buttonGenerate_clicked(self, widget): print "You clicked the button" app = QueryRelevanceEvaluationApp() gtk.main() And the foo.glade file: <?xml version="1.0"?> <interface> <requires lib="gtk+" version="2.16"/> <!-- interface-naming-policy project-wide --> <object class="GtkWindow" id="windowRelevanceEvaluation"> <property name="visible">True</property> <property name="title" translatable="yes">Query Result Relevance Evaluation</property> <child> <object class="GtkVBox" id="vbox1"> <property name="visible">True</property> <property name="orientation">vertical</property> <child> <object class="GtkHBox" id="hbox2"> <property name="visible">True</property> <child> <object class="GtkLabel" id="labelQuery"> <property name="visible">True</property> <property name="label" translatable="yes">Query:</property> </object> <packing> <property name="expand">False</property> <property name="padding">4</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkEntry" id="entry1"> <property name="visible">True</property> <property name="can_focus">True</property> <property name="invisible_char">&#x25CF;</property> </object> <packing> <property name="padding">4</property> <property name="position">1</property> </packing> </child> </object> <packing> <property name="position">0</property> </packing> </child> <child> <object class="GtkFrame" id="frameSource"> <property name="visible">True</property> <property name="label_xalign">0</property> <child> <object class="GtkAlignment" id="alignment1"> <property name="visible">True</property> <property name="left_padding">12</property> <child> <object class="GtkHButtonBox" id="hbuttonbox1"> <property name="visible">True</property> <child> <object class="GtkRadioButton" id="radiobuttonGoogle"> <property name="label" translatable="yes">Google</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkRadioButton" id="radiobuttonBing"> <property name="label" translatable="yes">Bing</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">1</property> </packing> </child> <child> <object class="GtkRadioButton" id="radiobuttonBoden"> <property name="label" translatable="yes">Boden</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">2</property> </packing> </child> <child> <object class="GtkRadioButton" id="radiobuttonCSV"> <property name="label" translatable="yes">CSV</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">3</property> </packing> </child> </object> </child> </object> </child> <child type="label"> <object class="GtkLabel" id="labelFrameSource"> <property name="visible">True</property> <property name="label" translatable="yes">&lt;b&gt;Source&lt;/b&gt;</property> <property name="use_markup">True</property> </object> </child> </object> <packing> <property name="position">1</property> </packing> </child> <child> <object class="GtkFrame" id="frame1"> <property name="visible">True</property> <property name="label_xalign">0</property> <child> <object class="GtkHBox" id="hbox3"> <property name="visible">True</property> <child> <object class="GtkLabel" id="labelResults"> <property name="visible">True</property> <property name="label" translatable="yes">Number Results:</property> </object> <packing> <property name="expand">False</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkSpinButton" id="spinbuttonResults"> <property name="visible">True</property> <property name="can_focus">True</property> <property name="invisible_char">&#x25CF;</property> </object> <packing> <property name="padding">4</property> <property name="position">1</property> </packing> </child> </object> </child> <child type="label"> <object class="GtkLabel" id="labelFrameResults"> <property name="visible">True</property> <property name="label" translatable="yes">&lt;b&gt;Results&lt;/b&gt;</property> <property name="use_markup">True</property> </object> </child> </object> <packing> <property name="padding">2</property> <property name="position">2</property> </packing> </child> <child> <object class="GtkButton" id="buttonGenerateResults"> <property name="label" translatable="yes">Generate!</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">True</property> </object> <packing> <property name="position">3</property> </packing> </child> </object> </child> </object> </interface> foo.glade and the above python script are in the same directory, and I have tried using a fully-qualified path but still get the same error (I am certain that the path is correct!). Any ideas? Cheers, Pete

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• Assigning property to JS object using another objects property value as the property name

  - by hamstar

  Hey guys, I want to use the value of an objects property to name the property of another object. Easy to do in PHP: $object1->property = 'name'; $object2->{$object1->property} = "value"; echo $object2->name; //outputs "value" But in Javascript I can't figure out how to do this. The curly braces are used a different way. Anyone know the php equivalent in javascript? Thanks :)

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• About Intellectual-Property agreement with employer

  - by turbo

  In IP agreement IP is define as below Intellectual Property (whether or not patentable and whether or not made during working hours) is defined as but not limited to: all product specifications, developments, inventions, works of authorship, derivative works, technologies, programs, systems, software, mobile applications and other mobile programming interfaces, designs, methodologies, encryptions, ideas, techniques, patents, formulas, processes, concepts, know-how and date made or conceived or reduced to practice or developed during employment period ,remain the property of XXXXXXX[COMPANY_NAME]XXXX or its affiliates. This is the first time I have seen any IP agreement. Isn't it too stringent? or its standard practice across industry?

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• C#: access a class property when the property identifier is known as a string

  - by Hans

  Hi, I'm using LINQ to Entities on a database which structure is not known in advance. I use reflection to retrieve the information, and now have a list of strings with all the table names. Because I use LINQ, I also have the datasource encapsulated in a C# class (linqContext), with each table being a property of that class. What I want to achieve is this: Assume one of the strings in the table names list is "Employees". This is known in code, I want to do the following: linqContext.Employees.DoSomethingHere(); Is this possible? I know that if all the propertie were just items in a list, I could use the string as indexer, linqContext["Employees"]. However, this is not the case :(

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• Intellectual Property for in house development

  - by Kyle Rogers

  My company is a sub contractor on a major government contract. Over the past 5 years we've been developing in house applications to help support our company and streamline our work. Apparently in 2008 our president of the company at that time signed a continuation of services contract with the company we subcontract with on this project. In the contract amendment various things were discussed such as intellectual property and the creation of new and existing tools. The contract states that all the subcontractor's tools/scripts/etc... become the intellectual property of the main contractor holder. Basically all tools that were created in support of the project which we work on are no longer ours exclusively and they have rights to them. My company really doesn't do software development specifically but because of this contract these tools helped tremendously with our daily tasking. Does my company have any sort of recourse or actions to help keep our tools? My team of developers were completely unaware of any of these negotiations and until recently were kept in the dark about the agreements that were made. Do we as developers have any rights to the software? Since our company is not a software development shop, we have created all these tools without any sort of agreements or contracts within the company stating that we give our company full rights to our creations? I was reading an article by Joel Spolsky on this topic and was just wonder if there is any advice out there to help assist us? Thank you Joel Spolsky's Article

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• Segmentation fault when running a python script/GTKBuilder app?

  - by pythonscript

  I'm trying to learn GUI programming using python2 and GTKBuilder, but I get a segmentation fault when I run the code. This is my file, created in Glade as a GTKBuilder file: <?xml version="1.0" encoding="UTF-8"?> <interface> <!-- interface-requires gtk+ 3.0 --> <object class="GtkWindow" id="mainWindow"> <property name="can_focus">False</property> <child> <object class="GtkBox" id="box1"> <property name="visible">True</property> <property name="can_focus">False</property> <property name="orientation">vertical</property> <child> <object class="GtkBox" id="box2"> <property name="visible">True</property> <property name="can_focus">False</property> <property name="halign">start</property> <property name="margin_left">146</property> <property name="margin_right">276</property> <child> <object class="GtkLabel" id="label1"> <property name="visible">True</property> <property name="can_focus">False</property> <property name="label" translatable="yes">label</property> </object> <packing> <property name="expand">True</property> <property name="fill">False</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkEntry" id="entryName"> <property name="visible">True</property> <property name="can_focus">True</property> <property name="margin_bottom">4</property> <property name="hexpand">True</property> <property name="vexpand">True</property> <property name="invisible_char">?</property> <property name="placeholder_text">Please enter your name here...</property> </object> <packing> <property name="expand">True</property> <property name="fill">True</property> <property name="position">1</property> </packing> </child> </object> <packing> <property name="expand">False</property> <property name="fill">True</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkButton" id="buttonWriteNameToFile"> <property name="label" translatable="yes">button</property> <property name="use_action_appearance">False</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">True</property> <property name="use_action_appearance">False</property> <signal name="clicked" handler="buttonWriteNameToFile_clicked" swapped="no"/> </object> <packing> <property name="expand">False</property> <property name="fill">True</property> <property name="position">1</property> </packing> </child> <child> <placeholder/> </child> <child> <placeholder/> </child> </object> </child> </object> </interface> My python code, based on this question, is this: #!/usr/bin/env python import gtk class NameApp: def __init__(self): filename = "project.glade" builder = gtk.Builder() builder.add_from_file(filename) builder.connect_signals(self) builder.get_object("mainWindow").show_all() def buttonWriteNameToFile_clicked(self, widget): print("File write code...") if __name__ == "__main__": app = NameApp() gtk.main() Running the file with python2 yields this error: name.py:9: Warning: cannot create instance of abstract (non-instantiatable) type `GtkBox' builder.add_from_file(filename) ./geany_run_script.sh: line 5: 14897 Segmentation fault python2 "name.py" I thought I followed that example as closely as possible, and I don't see any differences outside of the GTKBuilder file. However, the example in the linked question runs successfully on my machine. I don't know if it's relevant, but I'm running Arch Linux x86_64.

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• Employers and intellectual property 2

  - by Rick

  I have a question about intellectual property, I am currently a manager in a small manufacturing firm. The owners are driven by greed and don't appreciate the development process of complex machinery and are happy just to send things out half done. I on the other hand think that it should be done properly as breakdown in the field can be costly, embarrassing. They seem to have all of us running around doing most of the work out of hours using the attitude of "Be grateful to have a job" yet no one has a contract or any security or any agreement in place. For a couple of the projects i am using PLC's and doing the code in my own time and the testing during company time, and i am aware that they cannot support their own machines if i left, but as i created the code in my own time who owns it? The have asked my to put in a shutdown code for a maintenance request after a given length of time, could this be classed as criminal damage or anything illegal apart from immoral? (we sell the machines with 12 month warrantee, shut down after) But as time goes on I'm getting rather fed up of the companies attitude toward the client. I am considering keeping the clients as my own and get them to contact me directly In the shutdown code. By doing something like this is a trial version contact me for a full license? I wouldn't feel bad for my current employer as he is not afraid to S***t on people as he has been evolved in numerous law suits and has over 30 failed companies leaving people and customers high and dry, we have took the company this far on the reputation of the workers and and i can see things heading like all the other companies he has owned and taking our reputations with him. So i suppose now i have set the scene, if i code into it to contact me directly in the shutdown could there be any legal impact on me, as i rightly or wrongly think i own the code and designs? Cheers R

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• ReSharper C# Live Template for Dependency Property and Property Change Routed Event Boilerplate Code

  - by Bart Read

  I don't know about you but it took me about 5 seconds to get royally fed up of typing the boilerplate code necessary for creating WPF (and Silverlight) dependency properties and, if you want them, their associated property change routed events. Being a ReSharper user, I wondered if there was any live template for doing this. It turns out there's nothing built in, but there are many examples of templates for creating dependency properties out there on the web, such as this excellent one from Roy...(read more)

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• how protect intellectual property when oursourcing software development?

  - by gkdsp

  I'm a small company needing to outsource software development. I've written both functional and technical specifications for GUI developers and back-end (C or PHP) developers to implement my software application. I'm a little nervous handing over copies of these documents to request bids from numerous companies. Looking for recommendations to protect my work while outsourcing. What's the conventional wisdom? Is there generic NDA someone could send me a link to. How do others handle this situation. What would the outsource companies expect, or not expect, from me?

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• Intellectual-Property Question

  - by Roger J. J.

  Like almost everyone here, I have a handfull of scripts and software that I have developed and am enthused about. I will be looking for my first job as a software designer / coder. It seems natural that I will be eager to please my employer and use scripts or similar methods that I have developed and worked for me in the past to please my employer. It seems certain that many things that I code will look very similar to things I have coded in the past. I don't understand how to document and articulate to an employer that this code base was mine before I got here and this will continue to be mine when I leave. Surely, this is a common issue, but none of the various searches I've done on the net have produced an answer to this question. How is this situation commonly dealt with in the industry? I feel like there should be a digital version of sending myself a 'certified letter' with my code/software/scripts contained. I'm not trying to protect my code from others using it; I am trying to protect my right to continue using my code base that I have developed prior to to gaining employment with an employer.

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• Demystifying Silverlight Dependency Properties

  - by dwahlin

  I have the opportunity to teach a lot of people about Silverlight (amongst other technologies) and one of the topics that definitely confuses people initially is the concept of dependency properties. I confess that when I first heard about them my initial thought was “Why do we need a specialized type of property?” While you can certainly use standard CLR properties in Silverlight applications, Silverlight relies heavily on dependency properties for just about everything it does behind the scenes. In fact, dependency properties are an essential part of the data binding, template, style and animation functionality available in Silverlight. They simply back standard CLR properties. In this post I wanted to put together a (hopefully) simple explanation of dependency properties and why you should care about them if you’re currently working with Silverlight or looking to move to it.   What are Dependency Properties? XAML provides a great way to define layout controls, user input controls, shapes, colors and data binding expressions in a declarative manner. There’s a lot that goes on behind the scenes in order to make XAML work and an important part of that magic is the use of dependency properties. If you want to bind data to a property, style it, animate it or transform it in XAML then the property involved has to be a dependency property to work properly. If you’ve ever positioned a control in a Canvas using Canvas.Left or placed a control in a specific Grid row using Grid.Row then you’ve used an attached property which is a specialized type of dependency property. Dependency properties play a key role in XAML and the overall Silverlight framework. Any property that you bind, style, template, animate or transform must be a dependency property in Silverlight applications. You can programmatically bind values to controls and work with standard CLR properties, but if you want to use the built-in binding expressions available in XAML (one of my favorite features) or the Binding class available through code then dependency properties are a necessity. Dependency properties aren’t needed in every situation, but if you want to customize your application very much you’ll eventually end up needing them. For example, if you create a custom user control and want to expose a property that consumers can use to change the background color, you have to define it as a dependency property if you want bindings, styles and other features to be available for use. Now that the overall purpose of dependency properties has been discussed let’s take a look at how you can create them. Creating Dependency Properties When .NET first came out you had to write backing fields for each property that you defined as shown next: Brush _ScheduleBackground; public Brush ScheduleBackground { get { return _ScheduleBackground; } set { _ScheduleBackground = value; } } Although .NET 2.0 added auto-implemented properties (for example: public Brush ScheduleBackground { get; set; }) where the compiler would automatically generate the backing field used by get and set blocks, the concept is still the same as shown in the above code; a property acts as a wrapper around a field. Silverlight dependency properties replace the _ScheduleBackground field shown in the previous code and act as the backing store for a standard CLR property. The following code shows an example of defining a dependency property named ScheduleBackgroundProperty: public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), null);   Looking through the code the first thing that may stand out is that the definition for ScheduleBackgroundProperty is marked as static and readonly and that the property appears to be of type DependencyProperty. This is a standard pattern that you’ll use when working with dependency properties. You’ll also notice that the property explicitly adds the word “Property” to the name which is another standard you’ll see followed. In addition to defining the property, the code also makes a call to the static DependencyProperty.Register method and passes the name of the property to register (ScheduleBackground in this case) as a string. The type of the property, the type of the class that owns the property and a null value (more on the null value later) are also passed. In this example a class named Scheduler acts as the owner. The code handles registering the property as a dependency property with the call to Register(), but there’s a little more work that has to be done to allow a value to be assigned to and retrieved from the dependency property. The following code shows the complete code that you’ll typically use when creating a dependency property. You can find code snippets that greatly simplify the process of creating dependency properties out on the web. The MVVM Light download available from http://mvvmlight.codeplex.com comes with built-in dependency properties snippets as well. public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), null); public Brush ScheduleBackground { get { return (Brush)GetValue(ScheduleBackgroundProperty); } set { SetValue(ScheduleBackgroundProperty, value); } } The standard CLR property code shown above should look familiar since it simply wraps the dependency property. However, you’ll notice that the get and set blocks call GetValue and SetValue methods respectively to perform the appropriate operation on the dependency property. GetValue and SetValue are members of the DependencyObject class which is another key component of the Silverlight framework. Silverlight controls and classes (TextBox, UserControl, CompositeTransform, DataGrid, etc.) ultimately derive from DependencyObject in their inheritance hierarchy so that they can support dependency properties. Dependency properties defined in Silverlight controls and other classes tend to follow the pattern of registering the property by calling Register() and then wrapping the dependency property in a standard CLR property (as shown above). They have a standard property that wraps a registered dependency property and allows a value to be assigned and retrieved. If you need to expose a new property on a custom control that supports data binding expressions in XAML then you’ll follow this same pattern. Dependency properties are extremely useful once you understand why they’re needed and how they’re defined. Detecting Changes and Setting Defaults When working with dependency properties there will be times when you want to assign a default value or detect when a property changes so that you can keep the user interface in-sync with the property value. Silverlight’s DependencyProperty.Register() method provides a fourth parameter that accepts a PropertyMetadata object instance. PropertyMetadata can be used to hook a callback method to a dependency property. The callback method is called when the property value changes. PropertyMetadata can also be used to assign a default value to the dependency property. By assigning a value of null for the final parameter passed to Register() you’re telling the property that you don’t care about any changes and don’t have a default value to apply. Here are the different constructor overloads available on the PropertyMetadata class: PropertyMetadata Constructor Overload Description PropertyMetadata(Object) Used to assign a default value to a dependency property. PropertyMetadata(PropertyChangedCallback) Used to assign a property changed callback method. PropertyMetadata(Object, PropertyChangedCalback) Used to assign a default property value and a property changed callback.   There are many situations where you need to know when a dependency property changes or where you want to apply a default. Performing either task is easily accomplished by creating a new instance of the PropertyMetadata class and passing the appropriate values to its constructor. The following code shows an enhanced version of the initial dependency property code shown earlier that demonstrates these concepts: public Brush ScheduleBackground { get { return (Brush)GetValue(ScheduleBackgroundProperty); } set { SetValue(ScheduleBackgroundProperty, value); } } public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), new PropertyMetadata(new SolidColorBrush(Colors.LightGray), ScheduleBackgroundChanged)); private static void ScheduleBackgroundChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var scheduler = d as Scheduler; scheduler.Background = e.NewValue as Brush; } The code wires ScheduleBackgroundProperty to a property change callback method named ScheduleBackgroundChanged. What’s interesting is that this callback method is static (as is the dependency property) so it gets passed the instance of the object that owns the property that has changed (otherwise we wouldn’t be able to get to the object instance). In this example the dependency object is cast to a Scheduler object and its Background property is assigned to the new value of the dependency property. The code also handles assigning a default value of LightGray to the dependency property by creating a new instance of a SolidColorBrush. To Sum Up In this post you’ve seen the role of dependency properties and how they can be defined in code. They play a big role in XAML and the overall Silverlight framework. You can think of dependency properties as being replacements for fields that you’d normally use with standard CLR properties. In addition to a discussion on how dependency properties are created, you also saw how to use the PropertyMetadata class to define default dependency property values and hook a dependency property to a callback method. The most important thing to understand with dependency properties (especially if you’re new to Silverlight) is that they’re needed if you want a property to support data binding, animations, transformations and styles properly. Any time you create a property on a custom control or user control that has these types of requirements you’ll want to pick a dependency property over of a standard CLR property with a backing field. There’s more that can be covered with dependency properties including a related property called an attached property….more to come.

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• .NET custom property attribute?

  - by ropstah

  EDIT: I'd better rephrase: How can I shift the GET-implementation of a Class property to a / using a custom attribute? (I've added instantation vars (classname, propertyname) to the attribute, however I'd rather have these automatically fetched ofcourse.) Public Class CustomClass <CustomAttributeClass(ClassName:="CustomClass", PropertyName = "SomeProperty")> _ Public Property SomeProperty() as String Get() as String //This implementation should be handled by the attribute class End Get Set(Byval value as String) Me._someProperty = value End Set End Property End Class Old question: I want to create a custom property attribute for classes. I can create a class derived from Attribute, and 'mark' the property with the attribute, but where to go from here? I have a repository where I can quickly get data based on the attributes values. I would like to generalize the behaviour of the property in the attribute but I don't know how to go from here... Any help would be greatly accepted! Public Class CustomDataAttribute : Inherits Attribute Private _name As String Public Sub New(ByVal name As String) Me.Name = name End Sub Property Name() As String Get Return _name End Get Set(ByVal value As String) Me._name = value End Set End Property End Class Public Class CustomClass <CustomDataAttribute(Name:="CustomField")> _ Public Property CustomField() End Property End Class

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• objective c- property

  - by Amir

  Hello all , I think i am missing somthing with property attributes. first i cant understand the different between retain and assign? If i use assign does the property increase the retain counter by 1 to the setter and also to the getter, and i need to use release to both of them? and how this work with readwrite or copy? from the view of retain count. I am trying to understand when i need to use release after working with property(setter and getter) @property (readwrite,assign) int iVar; what does assing do here?? what is the different between : @property (readwrite,assign) int iVar; to @property (readwrite,retain) int iVar; to @property (readwrite) int iVar; many thanks...

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• SQLAlchemy - how to map against a read-only (or calculated) property

  - by Jeff Peck

  I'm trying to figure out how to map against a simple read-only property and have that property fire when I save to the database. A contrived example should make this more clear. First, a simple table: meta = MetaData() foo_table = Table('foo', meta, Column('id', String(3), primary_key=True), Column('description', String(64), nullable=False), Column('calculated_value', Integer, nullable=False), ) What I want to do is set up a class with a read-only property that will insert into the calculated_value column for me when I call session.commit()... import datetime def Foo(object): def __init__(self, id, description): self.id = id self.description = description @property def calculated_value(self): self._calculated_value = datetime.datetime.now().second + 10 return self._calculated_value According to the sqlalchemy docs, I think I am supposed to map this like so: mapper(Foo, foo_table, properties = { 'calculated_value' : synonym('_calculated_value', map_column=True) }) The problem with this is that _calculated_value is None until you access the calculated_value property. It appears that SQLAlchemy is not calling the property on insertion into the database, so I'm getting a None value instead. What is the correct way to map this so that the result of the "calculated_value" property is inserted into the foo table's "calculated_value" column?

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• When to use "property" builtin: auxiliary functions and generators

  - by Seth Johnson

  I recently discovered Python's property built-in, which disguises class method getters and setters as a class's property. I'm now being tempted to use it in ways that I'm pretty sure are inappropriate. Using the property keyword is clearly the right thing to do if class A has a property _x whose allowable values you want to restrict; i.e., it would replace the getX() and setX() construction one might write in C++. But where else is it appropriate to make a function a property? For example, if you have class Vertex(object): def __init__(self): self.x = 0.0 self.y = 1.0 class Polygon(object): def __init__(self, list_of_vertices): self.vertices = list_of_vertices def get_vertex_positions(self): return zip( *( (v.x,v.y) for v in self.vertices ) ) is it appropriate to add vertex_positions = property( get_vertex_positions ) ? Is it ever ok to make a generator look like a property? Imagine if a change in our code meant that we no longer stored Polygon.vertices the same way. Would it then be ok to add this to Polygon? @property def vertices(self): for v in self._new_v_thing: yield v.calculate_equivalent_vertex()

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• Property hiding and reflection (C#)

  - by tehMick

  Declaring a property in a derived class that matches the name of a property in the base class "hides" it (unless it overrides it with the override keyword). Both the base and derived class properties will be returned by Type.GetProperties() if their types don't match. However, if their types do match, shockingly only the derived class's property is returned. For instance: class A { protected double p; public int P { get { return (int)p; } set { p = value; } } } class B : A { public new int P { get { return (int)p; } set { p = value; } } } class C : B { public new float P { get { return (float)p; } set { p = value; } } } Calling typeof(C).GetProperties() will only return B.P and C.P. Is it possible to call GetProperties() in a way that returns all three? There is almost certainly a way to do it by traversing the inheritance hierarchy, but is there a cleaner solution?

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• Property being immediately reset by ApplicationSetting Property Binding

  - by Slider345

  I have a .net 2.0 windows application written in c#, which currently uses several project settings to store user configurations. The forms in the application are made up of lots of user controls, each of which have properties that need to be set to these project settings. Right now these settings are manually assigned to the user control properties. I was hoping to simplify the code by replacing the manual implementation with ApplicationSettings Property Bindings. However, my first property is not behaving properly at all. The setting is an integer, used to record a port number typed into a text box. The setting is bound to an integer property on a user control, and that property sets the Text property on a TextBox control. When I type a new value into the textbox at runtime, as soon as the textbox loses focus, it is immediately replaced by the original value. A breakpoint on the property shows that it is immediately setting the property to the setting from the properties collection after I set it. Can anyone see what I'm doing wrong? Here's some code: The setting: [global::System.Configuration.UserScopedSettingAttribute()] [global::System.Diagnostics.DebuggerNonUserCodeAttribute()] [global::System.Configuration.DefaultSettingValueAttribute("1000")] public int Port { get{ return ((int)(this["Port"])); } set{ this["Port"] = value; } } The binding: this.ctrlNetworkConfig.DataBindings.Add(new System.Windows.Forms.Binding("PortNumber", global::TestProject.Properties.Settings.Default, "Port", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged)); this.ctrlNetworkConfig.PortNumber = global::TestProject.Properties.Settings.Default.Port; And lastly, the property on the user control: public int PortNumber { get{ int port; if(int.TryParse(this.txtPortNumber.Text, out port)) return port; else return 0; } set{ txtPortNumber.Text = value.ToString(); } } Any thoughts? Thanks in advance for your help. EDIT: Sorry about the formatting, trying to correct.

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• Conflict When Two Storyboards Sets the Opacity Property?

  - by kennethkryger

  Hi, Background: I have a WPF UserControl (MainControl - not shown in code below) that contains another one (called MyControl in the code below). MainControl has it's DataContext set to an object, that has a Project-property. When MainControl loads, the Project-property is always null. The problem: When MainControl loads, I want to fade in the MyControl using a special storyboard (only used this one time (this "specialFadeInStoryboard" changes Opacity-property of MyControl from 0 to 1). When the Project-property is set to a value other than null, I want the MyControl to fade out using the "fadeOutStoryboard" (changes Opacity-property of MyControl to 0) and if it's set to null afterwards I want to fade it in again this time using the "fadeInStoryboard" (changes Opacity-property of MyControl to 1). However, after adding the code for the "specialFadeInStoryboard", the MyControl is never faded out... What am I doing wrong? <local:MyControl Visibility="{Binding RelativeSource={RelativeSource Self}, Path=Opacity, Converter={StaticResource opacityToVisibilityConverter}, Mode=OneWay}"> <local:MyControl.Style> <Style> <Style.Triggers> <EventTrigger RoutedEvent="FrameworkElement.Loaded"> <BeginStoryboard Storyboard="{StaticResource specialFadeInStoryboard}"/> </EventTrigger> <DataTrigger Binding="{Binding Project, Converter={StaticResource nullToBooleanConverter}, Mode=OneWay}" Value="True"> <DataTrigger.EnterActions> <BeginStoryboard Storyboard="{StaticResource fadeOutStoryboard}"/> </DataTrigger.EnterActions> <DataTrigger.ExitActions> <BeginStoryboard Storyboard="{StaticResource fadeInStoryboard}"/> </DataTrigger.ExitActions> </DataTrigger> </Style.Triggers> </Style> </local:MyControl.Style> </local:MyControl>

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• Generic property- specify the type at runtime

  - by Lirik

  I was reading a question on making a generic property, but I'm a little confused at by the last example from the first answer (I've included the relevant code below): You have to know the type at compile time. If you don't know the type at compile time then you must be storing it in an object, in which case you can add the following property to the Foo class: public object ConvertedValue { get { return Convert.ChangeType(Value, Type); } } That's seems strange: it's converting the value to the specified type, but it's returning it as an object when the value was stored as an object. Doesn't the returned object still require un-boxing? If it does, then why bother with the conversion of the type? I'm also trying to make a generic property whose type will be determined at run time: public class Foo { object Value {get;set;} Type ValType{get;set;} Foo(object value, Type type) { Value = value; ValType = type; } // I need a property that is actually // returned as the specified value type... public object ConvertedValue { get { return Convert.ChangeType(Value, ValType); } } } Is it possible to make a generic property? Does the return property still require unboxing after it's accessed?

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• How to assign class property as display data memeber in datagridview

  - by KoolKabin

  hi guys, I am trying to display my data in datagridview. I created a class with different property and used its list as the datasource. it worked fine. but i got confused how to do that in case we have nested class. My Classes are as follows: class Category property UIN as integer property Name as string end class class item property uin as integer property name as string property mycategory as category end class my data list as follows: dim myDataList as list(of Item) = new List(of Item) myDataList.Add(new Item(1,"item1",new category(1,"cat1"))) myDataList.Add(new Item(2,"item2",new category(1,"cat1"))) myDataList.Add(new Item(3,"item3",new category(1,"cat1"))) myDataList.Add(new Item(4,"item4",new category(2,"cat2"))) myDataList.Add(new Item(5,"item5",new category(2,"cat2"))) myDataList.Add(new Item(6,"item6",new category(2,"cat2"))) Now I binded the datagridview control like: DGVMain.AutoGenerateColumns = False DGVMain.ColumnCount = 3 DGVMain.Columns(0).DataPropertyName = "UIN" DGVMain.Columns(0).HeaderText = "ID" DGVMain.Columns(1).DataPropertyName = "Name" DGVMain.Columns(1).HeaderText = "Name" DGVMain.Columns(2).DataPropertyName = "" **'here i want my category name** DGVMain.Columns(2).HeaderText = "category" DGVMain.datasource = myDataList DGVMain.refresh() I have tried using mycategory.name but it didn't worked. What can be done to get expected result? Is there any better idea other than this to accomplish the same task?

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• How to assign class property as display data member in datagridview

  - by KoolKabin

  hi guys, I am trying to display my data in datagridview. I created a class with different property and used its list as the datasource. it worked fine. but I got confused how to do that in case we have nested class. My Classes are as follows: class Category property UIN as integer property Name as string end class class item property uin as integer property name as string property mycategory as category end class my data list as follows: dim myDataList as list(of Item) = new List(of Item) myDataList.Add(new Item(1,"item1",new category(1,"cat1"))) myDataList.Add(new Item(2,"item2",new category(1,"cat1"))) myDataList.Add(new Item(3,"item3",new category(1,"cat1"))) myDataList.Add(new Item(4,"item4",new category(2,"cat2"))) myDataList.Add(new Item(5,"item5",new category(2,"cat2"))) myDataList.Add(new Item(6,"item6",new category(2,"cat2"))) Now I binded the datagridview control like: DGVMain.AutoGenerateColumns = False DGVMain.ColumnCount = 3 DGVMain.Columns(0).DataPropertyName = "UIN" DGVMain.Columns(0).HeaderText = "ID" DGVMain.Columns(1).DataPropertyName = "Name" DGVMain.Columns(1).HeaderText = "Name" DGVMain.Columns(2).DataPropertyName = "" **'here i want my category name** DGVMain.Columns(2).HeaderText = "category" DGVMain.datasource = myDataList DGVMain.refresh() I have tried using mycategory.name but it didn't worked. What can be done to get expected result? Is there any better idea other than this to accomplish the same task? Edited My question as per comment: I have checked the link given by u. It was nice n very usefull. Since the code was in c# i tried to convert it in vb. Everything went good but failed at a point of case sensitive and next one is that i had my nested class name itemcategory and my property name was category. there it arouse the problem. it didn't searched for category but it searched for itemcategory. so confused on it. My Code as follows: Private Sub DGVMain_CellFormatting(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) Handles DGVMain.CellFormatting Dim DGVMain As DataGridView = CType(sender, DataGridView) e.Value = EvaluateValue(DGVMain.Rows(e.RowIndex).DataBoundItem, DGVMain.Columns(e.ColumnIndex).DataPropertyName) End Sub Private Function EvaluateValue(ByRef myObj As Object, ByRef myProp As String) As String Dim Ret As String = "" Dim Props As System.Reflection.PropertyInfo() Dim PropA As System.Reflection.PropertyInfo Dim ObjA As Object If myProp.Contains(".") Then myProp = myProp.Substring(0, myProp.IndexOf(".")) Props = myObj.GetType().GetProperties() For Each PropA In Props ObjA = PropA.GetValue(myObj, New Object() {}) If ObjA.GetType().Name = myProp Then Ret = EvaluateValue(ObjA, myProp.Substring(myProp.IndexOf(".") + 1)) Exit For End If Next Else PropA = myObj.GetType().GetProperty(myProp) Ret = PropA.GetValue(myObj, New Object() {}).ToString() End If Return Ret End Function

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• Overloading stream insertion without violating information hiding?

  - by Chris

  I'm using yaml-cpp for a project. I want to overload the << and >> operators for some classes, but I'm having an issue grappling with how to "properly" do this. Take the Note class, for example. It's fairly boring: class Note { public: // constructors Note( void ); ~Note( void ); // public accessor methods void number( const unsigned long& number ) { _number = number; } unsigned long number( void ) const { return _number; } void author( const unsigned long& author ) { _author = author; } unsigned long author( void ) const { return _author; } void subject( const std::string& subject ) { _subject = subject; } std::string subject( void ) const { return _subject; } void body( const std::string& body ) { _body = body; } std::string body( void ) const { return _body; } private: unsigned long _number; unsigned long _author; std::string _subject; std::string _body; }; The << operator is easy sauce. In the .h: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ); And in the .cpp: YAML::Emitter& operator << ( YAML::Emitter& out, const Note& v ) { out << v.number() << v.author() << v.subject() << v.body(); return out; } No sweat. Then I go to declare the >> operator. In the .h: void operator >> ( const YAML::Node& node, Note& note ); But in the .cpp I get: void operator >> ( const YAML::Node& node, Note& note ) { node[0] >> ? node[1] >> ? node[2] >> ? node[3] >> ? return; } If I write things like node[0] >> v._number; then I would need to change the CV-qualifier to make all of the Note fields public (which defeats everything I was taught (by professors, books, and experience))) about data hiding. I feel like doing node[0] >> temp0; v.number( temp0 ); all over the place is not only tedious, error-prone, and ugly, but rather wasteful (what with the extra copies). Then I got wise: I attempted to move these two operators into the Note class itself, and declare them as friends, but the compiler (GCC 4.4) didn't like that: src/note.h:44: error: ‘YAML::Emitter& Note::operator<<(YAML::Emitter&, const Note&)’ must take exactly one argument src/note.h:45: error: ‘void Note::operator(const YAML::Node&, Note&)’ must take exactly one argument Question: How do I "properly" overload the >> operator for a class Without violating the information hiding principle? Without excessive copying?

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• WPF Property Data binding to negate the property

  - by azamsharp

  Is there any way to change the value of property at runtime in WPF data binding. Let's say my TextBox is bind to a IsAdmin property. Is there anyway I can change that property value in XAML to be !IsAdmin. I just want to negate the property so Valueconverter might be an overkill! NOTE: Without using ValueConverter

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• Problem with UserControl with custom Dependency Property

  - by Mathias Koch

  Hi, I'm writing a user control with a dependency property for a search text called SearchText. It is a dependency property because I want to allow consumers of the control to use data binding. The user control contains a WPF TextBox where the user can enter the search text. I could use data binding to connect the SearchText dependency property of the user control with the Text dependency property of the TextBox, but this binding only fires when the text box looses input focus. What I want is SearchText to be updated after every change of Text. So I have added a TextChanged event handler to the user control where I set SearchText to the value of Text. My Problem is, the SearchText binding doesn't work, the source never gets updated. What am I doing wrong? Here's the relevant part of the user controls code-behind: public partial class UserControlSearchTextBox : UserControl { public string SearchText { get { return (string)GetValue(SearchTextProperty); } set { SetValue(SearchTextProperty, value); } } public static readonly DependencyProperty SearchTextProperty = DependencyProperty.Register("SearchText", typeof(string), typeof(UserControlSearchTextBox), new UIPropertyMetadata("")); private void TextBox_TextChanged(object sender, TextChangedEventArgs e) { SearchText = ((TextBox)sender).Text; } ... } The window that contains an instance of the user control has its DataContext set to an object that has a property also called SearchText. <uc:UserControlSearchTextBox SearchText="{Binding SearchText}" /> The data context of the Window: public class DataSourceUserManual : DataSourceBase { private string _searchText; public string SearchText { get { return _searchText; } set { _searchText = value; ... OnPropertyChanged("SearchText"); } } } Unfortunately, this setter is not called when I type into the text box. Any ideas?

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• Static Property losing its value intermittently ?

  - by joedotnot

  Is there something fundamentally wrong with the following design, or can anyone see why would the static properties sometimes loose their values ? I have a class library project containing a class AppConfig; this class is consumed by a Webforms project. The skeleton of AppConfig class is as follows: Public Class AppConfig Implements IConfigurationSectionHandler Private Const C_KEY1 As String = "WebConfig.Key.1" Private Const C_KEY2 As String = "WebConfig.Key.2" Private Const C_KEY1_DEFAULT_VALUE as string = "Key1defaultVal" Private Const C_KEY2_DEFAULT_VALUE as string = "Key2defaultVal" Private Shared m_field1 As String Private Shared m_field2 As String Public Shared ReadOnly Property ConfigValue1() As String Get ConfigValue1= m_field1 End Get End Property Public Shared ReadOnly Property ConfigValue2() As String Get ConfigValue2 = m_field2 End Get End Property Public Shared Sub OnApplicationStart() m_field1 = ReadSetting(C_KEY1, C_KEY1_DEFAULT_VALUE) m_field2 = ReadSetting(C_KEY2, C_KEY1_DEFAULT_VALUE) End Sub Public Overloads Shared Function ReadSetting(ByVal key As String, ByVal defaultValue As String) As String Try Dim setting As String = System.Configuration.ConfigurationManager.AppSettings(key) If setting Is Nothing Then ReadSetting = defaultValue Else ReadSetting = setting End If Catch ReadSetting = defaultValue End Try End Function Public Function Create(ByVal parent As Object, ByVal configContext As Object, ByVal section As System.Xml.XmlNode) As Object Implements System.Configuration.IConfigurationSectionHandler.Create Dim objSettings As NameValueCollection Dim objHandler As NameValueSectionHandler objHandler = New NameValueSectionHandler objSettings = CType(objHandler.Create(parent, configContext, section), NameValueCollection) Return 1 End Function End Class The Static Properties get set once on application start, from the Application_Start event of the Global.asax Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs) //Fires when the application is started AppConfig.OnApplicationStart() End Sub Thereafter, whenever we want to access a value in the Web.Config from anywhere, e.g. aspx page code-behind or another class or referenced class, we simply call the static property. For example, AppConfig.ConfigValue1() AppConfig.ConfigValue2() This is turn returns the value stored in the static backing fields m_field1, m_field2 Problem is sometimes these values are empty string, when clearly the Web.Config entry has values. Is there something fundamentally wrong with the above design, or is it reasonable to expect the static properties would keep their value for the life of the Application session?

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