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  • Some confusion with a class variable, but with a twist...

    - by Omega
    I have a class called MyPackage.WebServer and it has a property called DBEngine. I am also dynamically loading a module and class using load_module. Inside this class, it attempts to reference MyPackage.WebServer. When it does though, DBEngine is not set to the value given when WebServer is instantiated. It's the default (None). Would the fact that I'm using load_module cause a different object graph to be created and thus isolate my dynamically loaded class from the rest of my python app?

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  • "Public" nested classes or not

    - by Frederick
    Suppose I have a class 'Application'. In order to be initialised it takes certain settings in the constructor. Let's also assume that the number of settings is so many that it's compelling to place them in a class of their own. Compare the following two implementations of this scenario. Implementation 1: class Application { Application(ApplicationSettings settings) { //Do initialisation here } } class ApplicationSettings { //Settings related methods and properties here } Implementation 2: class Application { Application(Application.Settings settings) { //Do initialisation here } class Settings { //Settings related methods and properties here } } To me, the second approach is very much preferable. It is more readable because it strongly emphasises the relation between the two classes. When I write code to instantiate Application class anywhere, the second approach is going to look prettier. Now just imagine the Settings class itself in turn had some similarly "related" class and that class in turn did so too. Go only three such levels and the class naming gets out out of hand in the 'non-nested' case. If you nest, however, things still stay elegant. Despite the above, I've read people saying on StackOverflow that nested classes are justified only if they're not visible to the outside world; that is if they are used only for the internal implementation of the containing class. The commonly cited objection is bloating the size of containing class's source file, but partial classes is the perfect solution for that problem. My question is, why are we wary of the "publicly exposed" use of nested classes? Are there any other arguments against such use?

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  • XPath ordered priority attribute search

    - by user94000
    I want to write an XPath that can return some link elements on an HTML DOM. The syntax is wrong, but here is the gist of what I want: //web:link[@text='Login' THEN_TRY @href='login.php' THEN_TRY @index=0] THEN_TRY is a made-up operator, because I can't find what operator(s) to use. If many links exist on the page for the given set of [attribute=name] pairs, the link which matches the most left-most attribute(s) should be returned instead of any others. For example, consider a case where the above example XPath finds 3 links that match any of the given attributes: link A: text='Sign In', href='Login.php', index=0 link B: text='Login', href='Signin.php', index=15 link C: text='Login', href='Login.php', index=22 Link C ranks as the best match because it matches the First and Second attributes. Link B ranks second because it only matches the First attribute. Link A ranks last because it does not match the First attribute; it only matches the Second and Third attributes. The XPath should return the best match, Link C. If more than one link were tied for "best match", the XPath should return the first best link that it found on the page.

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  • How to change the attribute value of svg file

    - by rafiq7s
    Hello, In samplexml.svg there is a node <image width="744" height="1052" xlink:href="image1.png"/> I need to replace "image1.png" with another value like "image2.png". Please guide me with sample code how to to that. I could get the attribute value "image1.png". Here is the code: > <?php $xdoc = new DomDocument; > $xdoc->Load('samplexml.svg'); $tagName > = $xdoc->getElementsByTagName('image')->item(0); > $attribNode = > $tagName->getAttributeNode('xlink:href'); > > echo "Attribute Name : > ".$attribNode->name; echo "<br > />Attribute Value : > ".$attribNode->value; ?> Here is samplexml.svg: > <svg> <g> <title>Test title</title> > <image x="0" y="0" width="744" > height="1052" > xlink:href="image1.png"/> </g> </svg> Please help me, how to change this attribute value. Regards, rafiq7s

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  • Python: Inheritance of a class attribute (list)

    - by Sano98
    Hi everyone, inheriting a class attribute from a super class and later changing the value for the subclass works fine: class Unit(object): value = 10 class Archer(Unit): pass print Unit.value print Archer.value Archer.value = 5 print Unit.value print Archer.value leads to the output: 10 10 10 5 which is just fine: Archer inherits the value from Unit, but when I change Archer's value, Unit's value remains untouched. Now, if the inherited value is a list, the shallow copy effect strikes and the value of the superclass is also affected: class Unit(object): listvalue = [10] class Archer(Unit): pass print Unit.listvalue print Archer.listvalue Archer.listvalue[0] = 5 print Unit.listvalue print Archer.listvalue Output: 10 10 5 5 Is there a way to "deep copy" a list when inheriting it from the super class? Many thanks Sano

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  • Is It "Wrong"/Bad Design To Put A Thread/Background Worker In A Class?

    - by Jetti
    I have a class that will read from Excel (C# and .Net 4) and in that class I have a background worker that will load the data from Excel while the UI can remain responsive. My question is as follows: Is it bad design to have a background worker in a class? Should I create my class without it and use a background worker to operate on that class? I can't see any issues really of creating my class this way but then again I am a newbie so I figured I would make sure before I continue on. I hope that this question is relevant here as I don't think it should be on stackoverflow as my code works, this just a design issue.

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  • create a class attribute without going through __setattr__

    - by eric.frederich
    Hello, What I have below is a class I made to easily store a bunch of data as attributes. They wind up getting stored in a dictionary. I override __getattr__ and __setattr__ to store and retrieve the values back in different types of units. When I started overriding __setattr__ I was having trouble creating that initial dicionary in the 2nd line of __init__ like so... super(MyDataFile, self).__setattr__('_data', {}) My question... Is there an easier way to create a class level attribute with going through __setattr__? Also, should I be concerned about keeping a separate dictionary or should I just store everything in self.__dict__? #!/usr/bin/env python from unitconverter import convert import re special_attribute_re = re.compile(r'(.+)__(.+)') class MyDataFile(object): def __init__(self, *args, **kwargs): super(MyDataFile, self).__init__(*args, **kwargs) super(MyDataFile, self).__setattr__('_data', {}) # # For attribute type access # def __setattr__(self, name, value): self._data[name] = value def __getattr__(self, name): if name in self._data: return self._data[name] match = special_attribute_re.match(name) if match: varname, units = match.groups() if varname in self._data: return self.getvaras(varname, units) raise AttributeError # # other methods # def getvaras(self, name, units): from_val, from_units = self._data[name] if from_units == units: return from_val return convert(from_val, from_units, units), units def __str__(self): return str(self._data) d = MyDataFile() print d # set like a dictionary or an attribute d.XYZ = 12.34, 'in' d.ABC = 76.54, 'ft' # get it back like a dictionary or an attribute print d.XYZ print d.ABC # get conversions using getvaras or using a specially formed attribute print d.getvaras('ABC', 'cm') print d.XYZ__mm

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  • VB.NET class inherits a base class and implements an interface issue (works in C#)

    - by 300 baud
    I am trying to create a class in VB.NET which inherits a base abstract class and also implements an interface. The interface declares a string property called Description. The base class contains a string property called Description. The main class inherits the base class and implements the interface. The existence of the Description property in the base class fulfills the interface requirements. This works fine in C# but causes issues in VB.NET. First, here is an example of the C# code which works: public interface IFoo { string Description { get; set; } } public abstract class FooBase { public string Description { get; set; } } public class MyFoo : FooBase, IFoo { } Now here is the VB.NET version which gives a compiler error: Public Interface IFoo Property Description() As String End Interface Public MustInherit Class FooBase Private _Description As String Public Property Description() As String Get Return _Description End Get Set(ByVal value As String) _Description = value End Set End Property End Class Public Class MyFoo Inherits FooBase Implements IFoo End Class If I make the base class (FooBase) implement the interface and add the Implements IFoo.Description to the property all is good, but I do not want the base class to implement the interface. The compiler error is: Class 'MyFoo' must implement 'Property Description() As String' for interface 'IFoo'. Implementing property must have matching 'ReadOnly' or 'WriteOnly' specifiers. Can VB.NET not handle this, or do I need to change my syntax somewhere to get this to work?

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  • Accessing parent class attribute from sub-class body

    - by warwaruk
    I have a class Klass with a class attribute my_list. I have a subclass of it SubKlass, in which i want to have a class attribute my_list which is a modified version of the same attribute from parent class: class Klass(): my_list = [1, 2, 3] class SubKlass(Klass): my_list = Klass.my_list + [4, 5] # this works, but i must specify parent class explicitly #my_list = super().my_list + [4, 5] # SystemError: super(): __class__ cell not found #my_list = my_list + [4, 5] # NameError: name 'my_list' is not defined print(Klass.my_list) print(SubKlass.my_list) So, is there a way to access parent class attribute without specifying its name?

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  • Customer Attribute, not sorting select options

    - by Bosworth99
    Made a module that creates some customer EAV attributes. One of these attributes is a Select, and I'm dropping a bunch of options into their respective tables. Everything lines up and is accessible on both the front end and the back. Last thing before calling this part of things finished is the sort order of the options. They come out all scrambled, instead of the obvious default or alphabetical (seemingly at random... very wierd). I'm on Mage v1.11 (Pro/Enterprise). config.xml <config> <modules> <WACI_CustomerAttr> <version>0.1.0</version> </WACI_CustomerAttr> </modules> <global> <resources> <customerattr_setup> <setup> <module>WACI_CustomerAttr</module> <class>Mage_Customer_Model_Entity_Setup</class> </setup> <connection> <use>core_setup</use> </connection> </customerattr_setup> </resources> <models> <WACI_CustomerAttr> <class>WACI_CustomerAttr_Model</class> </WACI_CustomerAttr> </models> <fieldsets> <customer_account> <agency><create>1</create><update>1</update></agency> <title><create>1</create><update>1</update></title> <phone><create>1</create><update>1</update></phone> <mailing_address><create>1</create><update>1</update></mailing_address> <city><create>1</create><update>1</update></city> <state><create>1</create><update>1</update></state> <zip><create>1</create><update>1</update></zip> <fed_id><create>1</create><update>1</update></fed_id> <ubi><create>1</create><update>1</update></ubi> </customer_account> </fieldsets> </global> </config> mysql4-install-0.1.0.php <?php Mage::log('Installing WACI_CustomerAttr'); echo 'Running Upgrade: '.get_class($this)."\n <br /> \n"; //die ( 'its running' ); $installer = $this; /* @var $installer Mage_Customer_Model_Entity_Setup */ $installer->startSetup(); // bunch of attributes // State $installer->addAttribute('customer','state', array( 'type' => 'varchar', 'group' => 'Default', 'label' => 'State', 'input' => 'select', 'default' => 'Washington', 'source' => 'WACI_CustomerAttr/customer_attribute_data_select', 'global' => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_STORE, 'required' => true, 'visible' => true, 'user_defined' => 1, 'position' => 67 ) ); $attrS = Mage::getSingleton('eav/config')->getAttribute('customer', 'state'); $attrS->addData(array('sort_order'=>67)); $attrS->setData('used_in_forms', array('adminhtml_customer','customer_account_edit','customer_account_create'))->save(); $state_list = array('Alabama','Alaska','Arizona','Arkansas','California','Colorado','Connecticut','Delaware','Florida','Georgia', 'Hawaii','Idaho','Illinois','Indiana','Iowa','Kansas','Kentucky','Louisiana','Maine','Maryland','Massachusetts','Michigan', 'Minnesota','Mississippi','Missouri','Montana','Nebraska','Nevada','New Hampshire','New Jersey','New Mexico','New York', 'North Carolina','North Dakota','Ohio','Oklahoma','Oregon','Pennsylvania','Rhode Island','South Carolina','South Dakota', 'Tennessee','Texas','Utah','Vermont','Virginia','Washington','West Virginia','Wisconsin','Wyoming'); $aOption = array(); $aOption['attribute_id'] = $installer->getAttributeId('customer', 'state'); for($iCount=0;$iCount<sizeof($state_list);$iCount++){ $aOption['value']['option'.$iCount][0] = $state_list[$iCount]; } $installer->addAttributeOption($aOption); // a few more $installer->endSetup(); app/code/local/WACI/CustomerAttr/Model/Customer/Attribute/Data/Select.php <?php class WACI_CustomerAttr_Model_Customer_Attribute_Data_Select extends Mage_Eav_Model_Entity_Attribute_Source_Abstract{ function getAllOptions(){ if (is_null($this->_options)) { $this->_options = Mage::getResourceModel('eav/entity_attribute_option_collection') ->setAttributeFilter($this->getAttribute()->getId()) ->setStoreFilter($this->getAttribute()->getStoreId()) ->setPositionOrder('asc') ->load() ->toOptionArray(); } $options = $this->_options; return $options; } } theme/variation/template/persistent/customer/form/register.phtml <li> <?php $attribute = Mage::getModel('eav/config')->getAttribute('customer','state'); ?> <label for="state" class="<?php if($attribute->getIsRequired() == true){?>required<?php } ?>"><?php if($attribute->getIsRequired() == true){?><em>*</em><?php } ?><?php echo $this->__('State') ?></label> <div class="input-box"> <select name="state" id="state" class="<?php if($attribute->getIsRequired() == true){?>required-entry<?php } ?>"> <?php $options = $attribute->getSource()->getAllOptions(); foreach($options as $option){ ?> <option value='<?php echo $option['value']?>' <?php if($this->getFormData()->getState() == $option['value']){ echo 'selected="selected"';}?>><?php echo $this->__($option['label'])?></option> <?php } ?> </select> </div> </li> All options are getting loaded into table eav_attribute_option just fine (albeit without a sort_order defined), as well as table eav_attribute_option_value. In the adminhtml / customer-manage customers-account information this select is showing up fine (but its delivered automatically by the system). Seems I should be able to set the sort-order on creation of the attributeOptions, or, certainly, define the sort order in the data/select class. But nothing I've tried works. I'd rather not do a front-end hack either... Oh, and how do I set the default value of this select? (Different question, I know, but related). Setting the attributes 'default' = 'washington' seems to do nothing. There seem to be a lot of ways to set up attribute select options like this. Is there a better way that the one I've outlined here? Perhaps I'm messing something up. Cheers

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  • Display action-specific authorisation message for [Authorize] attribute

    - by FreshCode
    Is there a way to display an action-specific authorisation message for when an [Authorize] or [Authorize(Roles="Administrator")] attribute redirects the user to the sign-in page? Ideally, [Authorize(Roles="Administrator", Message="I'm sorry Dave. I'm afraid I can't let you do that.")] public ActionResult SomeAdminFunction() { // do admin stuff return View(); } As I understand it, attributes are not meant to add functionality, but this seems purely informational. One could do this inside the action, but it seems inelegant compared to the use of an attribute. Alternatively, if (!Request.IsAuthenticated) { if (!User.IsInRole("Administrator")) SetMessage("You need to be an administrator to destroy worlds."); // write message to session stack return RedirectToAction("SignIn", "Account"); } Is there an existing way to do this or do I need to override the [Authorize] attribute?

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  • C#: Making sure parameter has attribute

    - by slayerIQ
    I have an attribute lets call it SomeAttribute and a class i need to make sure the class is passed a type which has SomeAttribute. So this is how i do it now: public class Test() { public Test(SomeType obj) { if(!obj.GetType().IsDefined(typeof(SomeAttribute), false)) { throw new ArgumentException("Errormessage"); } } } But this means that i don't get any errors at compile time but somewhere at runtime, if obj does not have the attribute. Is there a way to specify in the method declaration that the parameter must have some attribute ? So i get errors i compile time when using the wrong parameters.

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  • Objective-C Class Question?

    - by tarnfeld
    Hey, My head is about to explode with this logic, can anyone help? Class A #imports Class B. Class A calls Method A in Class B. This works great Class B wants to send a response back to Class A from another method that is called from Method A. If you #import Class A from Class B, it is in effect an infinite loop and the whole thing crashes. Is there a way to do this properly, like a parent type thing? BTW, I'm developing for iPhone.

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  • Followup: Python 2.6, 3 abstract base class misunderstanding

    - by Aaron
    I asked a question at Python 2.6, 3 abstract base class misunderstanding. My problem was that python abstract base classes didn't work quite the way I expected them to. There was some discussion in the comments about why I would want to use ABCs at all, and Alex Martelli provided an excellent answer on why my use didn't work and how to accomplish what I wanted. Here I'd like to address why one might want to use ABCs, and show my test code implementation based on Alex's answer. tl;dr: Code after the 16th paragraph. In the discussion on the original post, statements were made along the lines that you don't need ABCs in Python, and that ABCs don't do anything and are therefore not real classes; they're merely interface definitions. An abstract base class is just a tool in your tool box. It's a design tool that's been around for many years, and a programming tool that is explicitly available in many programming languages. It can be implemented manually in languages that don't provide it. An ABC is always a real class, even when it doesn't do anything but define an interface, because specifying the interface is what an ABC does. If that was all an ABC could do, that would be enough reason to have it in your toolbox, but in Python and some other languages they can do more. The basic reason to use an ABC is when you have a number of classes that all do the same thing (have the same interface) but do it differently, and you want to guarantee that that complete interface is implemented in all objects. A user of your classes can rely on the interface being completely implemented in all classes. You can maintain this guarantee manually. Over time you may succeed. Or you might forget something. Before Python had ABCs you could guarantee it semi-manually, by throwing NotImplementedError in all the base class's interface methods; you must implement these methods in derived classes. This is only a partial solution, because you can still instantiate such a base class. A more complete solution is to use ABCs as provided in Python 2.6 and above. Template methods and other wrinkles and patterns are ideas whose implementation can be made easier with full-citizen ABCs. Another idea in the comments was that Python doesn't need ABCs (understood as a class that only defines an interface) because it has multiple inheritance. The implied reference there seems to be Java and its single inheritance. In Java you "get around" single inheritance by inheriting from one or more interfaces. Java uses the word "interface" in two ways. A "Java interface" is a class with method signatures but no implementations. The methods are the interface's "interface" in the more general, non-Java sense of the word. Yes, Python has multiple inheritance, so you don't need Java-like "interfaces" (ABCs) merely to provide sets of interface methods to a class. But that's not the only reason in software development to use ABCs. Most generally, you use an ABC to specify an interface (set of methods) that will likely be implemented differently in different derived classes, yet that all derived classes must have. Additionally, there may be no sensible default implementation for the base class to provide. Finally, even an ABC with almost no interface is still useful. We use something like it when we have multiple except clauses for a try. Many exceptions have exactly the same interface, with only two differences: the exception's string value, and the actual class of the exception. In many exception clauses we use nothing about the exception except its class to decide what to do; catching one type of exception we do one thing, and another except clause catching a different exception does another thing. According to the exception module's doc page, BaseException is not intended to be derived by any user defined exceptions. If ABCs had been a first class Python concept from the beginning, it's easy to imagine BaseException being specified as an ABC. But enough of that. Here's some 2.6 code that demonstrates how to use ABCs, and how to specify a list-like ABC. Examples are run in ipython, which I like much better than the python shell for day to day work; I only wish it was available for python3. Your basic 2.6 ABC: from abc import ABCMeta, abstractmethod class Super(): __metaclass__ = ABCMeta @abstractmethod def method1(self): pass Test it (in ipython, python shell would be similar): In [2]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods method1 Notice the end of the last line, where the TypeError exception tells us that method1 has not been implemented ("abstract methods method1"). That was the method designated as @abstractmethod in the preceding code. Create a subclass that inherits Super, implement method1 in the subclass and you're done. My problem, which caused me to ask the original question, was how to specify an ABC that itself defines a list interface. My naive solution was to make an ABC as above, and in the inheritance parentheses say (list). My assumption was that the class would still be abstract (can't instantiate it), and would be a list. That was wrong; inheriting from list made the class concrete, despite the abstract bits in the class definition. Alex suggested inheriting from collections.MutableSequence, which is abstract (and so doesn't make the class concrete) and list-like. I used collections.Sequence, which is also abstract but has a shorter interface and so was quicker to implement. First, Super derived from Sequence, with nothing extra: from abc import abstractmethod from collections import Sequence class Super(Sequence): pass Test it: In [6]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods __getitem__, __len__ We can't instantiate it. A list-like full-citizen ABC; yea! Again, notice in the last line that TypeError tells us why we can't instantiate it: __getitem__ and __len__ are abstract methods. They come from collections.Sequence. But, I want a bunch of subclasses that all act like immutable lists (which collections.Sequence essentially is), and that have their own implementations of my added interface methods. In particular, I don't want to implement my own list code, Python already did that for me. So first, let's implement the missing Sequence methods, in terms of Python's list type, so that all subclasses act as lists (Sequences). First let's see the signatures of the missing abstract methods: In [12]: help(Sequence.__getitem__) Help on method __getitem__ in module _abcoll: __getitem__(self, index) unbound _abcoll.Sequence method (END) In [14]: help(Sequence.__len__) Help on method __len__ in module _abcoll: __len__(self) unbound _abcoll.Sequence method (END) __getitem__ takes an index, and __len__ takes nothing. And the implementation (so far) is: from abc import abstractmethod from collections import Sequence class Super(Sequence): # Gives us a list member for ABC methods to use. def __init__(self): self._list = [] # Abstract method in Sequence, implemented in terms of list. def __getitem__(self, index): return self._list.__getitem__(index) # Abstract method in Sequence, implemented in terms of list. def __len__(self): return self._list.__len__() # Not required. Makes printing behave like a list. def __repr__(self): return self._list.__repr__() Test it: In [34]: a = Super() In [35]: a Out[35]: [] In [36]: print a [] In [37]: len(a) Out[37]: 0 In [38]: a[0] --------------------------------------------------------------------------- IndexError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() /home/aaron/projects/test/test.py in __getitem__(self, index) 10 # Abstract method in Sequence, implemented in terms of list. 11 def __getitem__(self, index): ---> 12 return self._list.__getitem__(index) 13 14 # Abstract method in Sequence, implemented in terms of list. IndexError: list index out of range Just like a list. It's not abstract (for the moment) because we implemented both of Sequence's abstract methods. Now I want to add my bit of interface, which will be abstract in Super and therefore required to implement in any subclasses. And we'll cut to the chase and add subclasses that inherit from our ABC Super. from abc import abstractmethod from collections import Sequence class Super(Sequence): # Gives us a list member for ABC methods to use. def __init__(self): self._list = [] # Abstract method in Sequence, implemented in terms of list. def __getitem__(self, index): return self._list.__getitem__(index) # Abstract method in Sequence, implemented in terms of list. def __len__(self): return self._list.__len__() # Not required. Makes printing behave like a list. def __repr__(self): return self._list.__repr__() @abstractmethod def method1(): pass class Sub0(Super): pass class Sub1(Super): def __init__(self): self._list = [1, 2, 3] def method1(self): return [x**2 for x in self._list] def method2(self): return [x/2.0 for x in self._list] class Sub2(Super): def __init__(self): self._list = [10, 20, 30, 40] def method1(self): return [x+2 for x in self._list] We've added a new abstract method to Super, method1. This makes Super abstract again. A new class Sub0 which inherits from Super but does not implement method1, so it's also an ABC. Two new classes Sub1 and Sub2, which both inherit from Super. They both implement method1 from Super, so they're not abstract. Both implementations of method1 are different. Sub1 and Sub2 also both initialize themselves differently; in real life they might initialize themselves wildly differently. So you have two subclasses which both "is a" Super (they both implement Super's required interface) although their implementations are different. Also remember that Super, although an ABC, provides four non-abstract methods. So Super provides two things to subclasses: an implementation of collections.Sequence, and an additional abstract interface (the one abstract method) that subclasses must implement. Also, class Sub1 implements an additional method, method2, which is not part of Super's interface. Sub1 "is a" Super, but it also has additional capabilities. Test it: In [52]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods method1 In [53]: a = Sub0() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Sub0 with abstract methods method1 In [54]: a = Sub1() In [55]: a Out[55]: [1, 2, 3] In [56]: b = Sub2() In [57]: b Out[57]: [10, 20, 30, 40] In [58]: print a, b [1, 2, 3] [10, 20, 30, 40] In [59]: a, b Out[59]: ([1, 2, 3], [10, 20, 30, 40]) In [60]: a.method1() Out[60]: [1, 4, 9] In [61]: b.method1() Out[61]: [12, 22, 32, 42] In [62]: a.method2() Out[62]: [0.5, 1.0, 1.5] [63]: a[:2] Out[63]: [1, 2] In [64]: a[0] = 5 --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: 'Sub1' object does not support item assignment Super and Sub0 are abstract and can't be instantiated (lines 52 and 53). Sub1 and Sub2 are concrete and have an immutable Sequence interface (54 through 59). Sub1 and Sub2 are instantiated differently, and their method1 implementations are different (60, 61). Sub1 includes an additional method2, beyond what's required by Super (62). Any concrete Super acts like a list/Sequence (63). A collections.Sequence is immutable (64). Finally, a wart: In [65]: a._list Out[65]: [1, 2, 3] In [66]: a._list = [] In [67]: a Out[67]: [] Super._list is spelled with a single underscore. Double underscore would have protected it from this last bit, but would have broken the implementation of methods in subclasses. Not sure why; I think because double underscore is private, and private means private. So ultimately this whole scheme relies on a gentleman's agreement not to reach in and muck with Super._list directly, as in line 65 above. Would love to know if there's a safer way to do that.

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  • how to COPY Attribute value in a new attribute

    - by Mukesh
    How to copy data of attribute to new attribute in the same column in sql original data <root> <child attr='hello'></child> </root> Result 1 <root> <child attr='hello' attr2='hello'></child> </root> Result 2(with a modification) <root> <child attr='hello' attr2='**H**ello **W**orld'></child> </root>

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  • XML databinding to TreeView (or Tab control), bind attribute based on different attribute

    - by Number8
    Hello, I have some xml: <Test> <thing location="home" status="good"/> <thing location=work" status="bad"/> <thing location="mountains" status="good"/> </Test> The leaves on the TreeView are the values of the status attribute; the nodes will be the value of the location attribute. +--bad ¦.....+--work +--good .......+--home .......+--mountains Currently, I populate the TreeView (or Tab control) manually, iterating through the xml, adding the nodes to the appropriate leaf. Can this be done via databinding? I'm guessing a Converter will be involved... Thanks for any advice.

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  • DataAnnotation attributes buddy class strangeness - ASP.NET MVC

    - by JK
    Given this POCO class that was automatically generated by an EntityFramework T4 template (has not and can not be manually edited in any way): public partial class Customer { [Required] [StringLength(20, ErrorMessage = "Customer Number - Please enter no more than 20 characters.")] [DisplayName("Customer Number")] public virtual string CustomerNumber { get;set; } [Required] [StringLength(10, ErrorMessage = "ACNumber - Please enter no more than 10 characters.")] [DisplayName("ACNumber")] public virtual string ACNumber{ get;set; } } Note that "ACNumber" is a badly named database field, so the autogenerator is unable to generate the correct display name and error message which should be "Account Number". So we manually create this buddy class to add custom attributes that could not be automatically generated: [MetadataType(typeof(CustomerAnnotations))] public partial class Customer { } public class CustomerAnnotations { [NumberCode] // This line does not work public virtual string CustomerNumber { get;set; } [StringLength(10, ErrorMessage = "Account Number - Please enter no more than 10 characters.")] [DisplayName("Account Number")] public virtual string ACNumber { get;set; } } Where [NumberCode] is a simple regex based attribute that allows only digits and hyphens: [AttributeUsage(AttributeTargets.Property)] public class NumberCodeAttribute: RegularExpressionAttribute { private const string REGX = @"^[0-9-]+$"; public NumberCodeAttribute() : base(REGX) { } } NOW, when I load the page, the DisplayName attribute works correctly - it shows the display name from the buddy class not the generated class. The StringLength attribute does not work correctly - it shows the error message from the generated class ("ACNumber" instead of "Account Number"). BUT the [NumberCode] attribute in the buddy class does not even get applied to the AccountNumber property: foreach (ValidationAttribute attrib in prop.Attributes.OfType<ValidationAttribute>()) { // This collection correctly contains all the [Required], [StringLength] attributes // BUT does not contain the [NumberCode] attribute ApplyValidation(generator, attrib); } Why does the prop.Attributes.OfType<ValidationAttribute>() collection not contain the [NumberCode] attribute? NumberCode inherits RegularExpressionAttribute which inherits ValidationAttribute so it should be there. If I manually move the [NumberCode] attribute to the autogenerated class, then it is included in the prop.Attributes.OfType<ValidationAttribute>() collection. So what I don't understand is why this particular attribute does not work in when in the buddy class, when other attributes in the buddy class do work. And why this attribute works in the autogenerated class, but not in the buddy. Any ideas? Also why does DisplayName get overriden by the buddy, when StringLength does not?

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  • Foolishness Check: PHP Class finds Class file but not Class in the file.

    - by Daniel Bingham
    I'm at a loss here. I've defined an abstract superclass in one file and a subclass in another. I have required the super-classes file and the stack trace reports to find an include it. However, it then returns an error when it hits the 'extends' line: Fatal error: Class 'HTMLBuilder' not found in View/Markup/HTML/HTML4.01/HTML4_01Builder.php on line 7. I had this working with another class tree that uses factories a moment ago. I just added the builder layer in between the factories and the consumer. The factory layer looked almost exactly the same in terms of includes and dependencies. So that makes me think I must have done something silly that's causes the HTMLBuilder.php file to not be included correctly or interpreted correctly or some such. Here's the full stack trace (paths slightly altered): # Time Memory Function Location 1 0.0001 53904 {main}( ) ../index.php:0 2 0.0002 67600 require_once( 'View/Page.php' ) ../index.php:3 3 0.0003 75444 require_once( 'View/Sections/SectionFactory.php' ) ../Page.php:4 4 0.0003 81152 require_once( 'View/Sections/HTML/HTMLSectionFactory.php' ) ../SectionFactory.php:3 5 0.0004 92108 require_once( 'View/Sections/HTML/HTMLTitlebarSection.php' ) ../HTMLSectionFactory.php:5 6 0.0005 99716 require_once( 'View/Markup/HTML/HTMLBuilder.php' ) ../HTMLTitlebarSection.php:3 7 0.0005 103580 require_once( 'View/Markup/MarkupBuilder.php' ) ../HTMLBuilder.php:3 8 0.0006 124120 require_once( 'View/Markup/HTML/HTML4.01/HTML4_01Builder.php' ) ../MarkupBuilder.php:3 Here's the code in question: Parent class (View/Markup/HTML/HTMLBuilder.php): <?php require_once('View/Markup/MarkupBuilder.php'); abstract class HTMLBuilder extends MarkupBuilder { public abstract function getLink($text, $href); public abstract function getImage($src, $alt); public abstract function getDivision($id, array $classes=NULL, array $children=NULL); public abstract function getParagraph($text, array $classes=NULL, $id=NULL); } ?> Child Class, (View/Markup/HTML/HTML4.01/HTML4_01Builder.php): <?php require_once('HTML4_01Factory.php'); require_once('View/Markup/HTML/HTMLBuilder.php'); class HTML4_01Builder extends HTMLBuilder { private $factory; public function __construct() { $this->factory = new HTML4_01Factory(); } public function getLink($href, $text) { $link = $this->factory->getA(); $link->addAttribute('href', $href); $link->addChild($this->factory->getText($text)); return $link; } public function getImage($src, $alt) { $image = $this->factory->getImg(); $image->addAttribute('src', $src); $image->addAttribute('alt', $alt); return $image; } public function getDivision($id, array $classes=NULL, array $children=NULL) { $div = $this->factory->getDiv(); $div->setID($id); if(!empty($classes)) { $div->addClasses($classes); } if(!empty($children)) { $div->addChildren($children); } return $div; } public function getParagraph($text, array $classes=NULL, $id=NULL) { $p = $this->factory->getP(); $p->addChild($this->factory->getText($text)); if(!empty($classes)) { $p->addClasses($classes); } if(!empty($id)) { $p->setID($id); } return $p; } } ?> I would appreciate any and all ideas. I'm at a complete loss here as to what is going wrong. I'm sure it's something stupid I just can't see...

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  • Prefer class members or passing arguments between internal methods?

    - by geoffjentry
    Suppose within the private portion of a class there is a value which is utilized by multiple private methods. Do people prefer having this defined as a member variable for the class or passing it as an argument to each of the methods - and why? On one hand I could see an argument to be made that reducing state (ie member variables) in a class is generally a good thing, although if the same value is being repeatedly used throughout a class' methods it seems like that would be an ideal candidate for representation as state for the class to make the code visibly cleaner if nothing else. Edit: To clarify some of the comments/questions that were raised, I'm not talking about constants and this isn't relating to any particular case rather just a hypothetical that I was talking to some other people about. Ignoring the OOP angle for a moment, the particular use case that I had in mind was the following (assume pass by reference just to make the pseudocode cleaner) int x doSomething(x) doAnotherThing(x) doYetAnotherThing(x) doSomethingElse(x) So what I mean is that there's some variable that is common between multiple functions - in the case I had in mind it was due to chaining of smaller functions. In an OOP system, if these were all methods of a class (say due to refactoring via extracting methods from a large method), that variable could be passed around them all or it could be a class member.

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  • Selecting element by data attribute

    - by zizo
    Is there an easy and straight-forward method to select elements based on their data attribute? For example, select all anchors that has data attribute named customerID which has value of 22. I am kind of hesitant to use rel or other attributes to store such information, but I find it much harder to select an element based on what data is stored in it. Thanks!

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  • Add attribute to embed tag using jquery

    - by Rob
    I have the following embed tag: <embed type="application/x-shockwave-flash" width="640" height="505" src="url_to_video" allowscriptaccess="always" allowfullscreen="true"></embed> I have about five of theses on a page, and I'd like to add the attribute wmode="opaque" to all of them. However, I tried to do it like this and it didnt' work: $j("embed").attr('wmode','opaque'); Is there another way I can dynamically set the attribute wmode="opaque" ? Thanks!

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  • change a frame's attribute by pressing a button

    - by asavu
    Hi. Suppose we have a JFrame named frame1 with a String attribute named credentials set inittially to null. I have a jButton named button1 attached to the frame and I want to change the frame1 String credentials attribute by pressing button1. I need some piece of advice regarding the ActionListener code especially. Could you guys pls help me? Thank you.

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  • MVC 3 AdditionalMetadata Attribute with ViewBag to Render Dynamic UI

    - by Steve Michelotti
    A few months ago I blogged about using Model metadata to render a dynamic UI in MVC 2. The scenario in the post was that we might have a view model where the questions are conditionally displayed and therefore a dynamic UI is needed. To recap the previous post, the solution was to use a custom attribute called [QuestionId] in conjunction with an “ApplicableQuestions” collection to identify whether each question should be displayed. This allowed me to have a view model that looked like this: 1: [UIHint("ScalarQuestion")] 2: [DisplayName("First Name")] 3: [QuestionId("NB0021")] 4: public string FirstName { get; set; } 5: 6: [UIHint("ScalarQuestion")] 7: [DisplayName("Last Name")] 8: [QuestionId("NB0022")] 9: public string LastName { get; set; } 10: 11: [UIHint("ScalarQuestion")] 12: [QuestionId("NB0023")] 13: public int Age { get; set; } 14: 15: public IEnumerable<string> ApplicableQuestions { get; set; } At the same time, I was able to avoid repetitive IF statements for every single question in my view: 1: <%: Html.EditorFor(m => m.FirstName, new { applicableQuestions = Model.ApplicableQuestions })%> 2: <%: Html.EditorFor(m => m.LastName, new { applicableQuestions = Model.ApplicableQuestions })%> 3: <%: Html.EditorFor(m => m.Age, new { applicableQuestions = Model.ApplicableQuestions })%> by creating an Editor Template called “ScalarQuestion” that encapsulated the IF statement: 1: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %> 2: <%@ Import Namespace="DynamicQuestions.Models" %> 3: <%@ Import Namespace="System.Linq" %> 4: <% 5: var applicableQuestions = this.ViewData["applicableQuestions"] as IEnumerable<string>; 6: var questionAttr = this.ViewData.ModelMetadata.ContainerType.GetProperty(this.ViewData.ModelMetadata.PropertyName).GetCustomAttributes(typeof(QuestionIdAttribute), true) as QuestionIdAttribute[]; 7: string questionId = null; 8: if (questionAttr.Length > 0) 9: { 10: questionId = questionAttr[0].Id; 11: } 12: if (questionId != null && applicableQuestions.Contains(questionId)) { %> 13: <div> 14: <%: Html.Label("") %> 15: <%: Html.TextBox("", this.Model)%> 16: </div> 17: <% } %> You might want to go back and read the full post in order to get the full context. MVC 3 offers a couple of new features that make this scenario more elegant to implement. The first step is to use the new [AdditionalMetadata] attribute which, so far, appears to be an under appreciated new feature of MVC 3. With this attribute, I don’t need my custom [QuestionId] attribute anymore - now I can just write my view model like this: 1: [UIHint("ScalarQuestion")] 2: [DisplayName("First Name")] 3: [AdditionalMetadata("QuestionId", "NB0021")] 4: public string FirstName { get; set; } 5:   6: [UIHint("ScalarQuestion")] 7: [DisplayName("Last Name")] 8: [AdditionalMetadata("QuestionId", "NB0022")] 9: public string LastName { get; set; } 10:   11: [UIHint("ScalarQuestion")] 12: [AdditionalMetadata("QuestionId", "NB0023")] 13: public int Age { get; set; } Thus far, the documentation seems to be pretty sparse on the AdditionalMetadata attribute. It’s buried in the Other New Features section of the MVC 3 home page and, after showing the attribute on a view model property, it just says, “This metadata is made available to any display or editor template when a product view model is rendered. It is up to you to interpret the metadata information.” But what exactly does it look like for me to “interpret the metadata information”? Well, it turns out it makes the view much easier to work with. Here is the re-implemented ScalarQuestion template updated for MVC 3 and Razor: 1: @{ 2: object questionId; 3: ViewData.ModelMetadata.AdditionalValues.TryGetValue("QuestionId", out questionId); 4: if (ViewBag.applicableQuestions.Contains((string)questionId)) { 5: <div> 6: @Html.LabelFor(m => m) 7: @Html.TextBoxFor(m => m) 8: </div> 9: } 10: } So we’ve gone from 17 lines of code (in the MVC 2 version) to about 7-8 lines of code here. The first thing to notice is that in MVC 3 we now have a property called “AdditionalValues” that hangs off of the ModelMetadata property. This is automatically populated by any [AdditionalMetadata] attributes on the property. There is no more need for me to explicitly write Reflection code to GetCustomAttributes() and then check to see if those attributes were present. I can just call TryGetValue() on the dictionary to see if they were present. Secondly, the “applicableQuestions” anonymous type that I passed in from the calling view – in MVC 3 I now have a dynamic ViewBag property where I can just “dot into” the applicableQuestions with a nicer syntax than dictionary square bracket syntax. And there’s no problems calling the Contains() method on this dynamic object because at runtime the DLR has resolved that it is a generic List<string>. At this point you might be saying that, yes the view got much nicer than the MVC 2 version, but my view model got slightly worse.  In the previous version I had a nice [QuestionId] attribute but now, with the [AdditionalMetadata] attribute, I have to type the string “QuestionId” for every single property and hope that I don’t make a typo. Well, the good news is that it’s easy to create your own attributes that can participate in the metadata’s additional values. The key is that the attribute must implement that IMetadataAware interface and populate the AdditionalValues dictionary in the OnMetadataCreated() method: 1: public class QuestionIdAttribute : Attribute, IMetadataAware 2: { 3: public string Id { get; set; } 4:   5: public QuestionIdAttribute(string id) 6: { 7: this.Id = id; 8: } 9:   10: public void OnMetadataCreated(ModelMetadata metadata) 11: { 12: metadata.AdditionalValues["QuestionId"] = this.Id; 13: } 14: } This now allows me to encapuslate my “QuestionId” string in just one place and get back to my original attribute which can be used like this: [QuestionId(“NB0021”)]. The [AdditionalMetadata] attribute is a powerful and under-appreciated new feature of MVC 3. Combined with the dynamic ViewBag property, you can do some really interesting things with your applications with less code and ceremony.

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