I've got the following code at the top of my CoffeeScript
program to reference a BinaryNode class from a BinaryTree
class.
Since I want to be able to use the BinaryTree class from
a node.js program or from the browser I have the following
if/else statement to reference the BinaryNode.
file: BinaryTree.coffee
isNodeJs = exports?
if isNodeJs
{BinaryNode} = require('./binary_node')
else
BinaryNode = window.BinaryNode
class BinaryTree
(code for BinaryTree goes here)
Somehow this if/else bugs me specially if I will need to
add it on a lot of different classes that make up the
program.
Are there any other better ways to perform this check?
(From my comment above)
The branching can be shortened to:
{BinaryNode} = require?("/.binary_node") or window
(provided you don't have a global require function somewhere in your browser code, of course)
Related
I use Enterprise Architect for code generation and I would like to automatically retrieve all tags (in my case Java annotations) of the interfaces that a class realizes. Consider the following example:
From this model, I want to generate a class that looks like this:
#AnnotationOfMyInterface
public class MyClass {
...
}
So I want to add annotations as tags to MyInterface that should be applied to MyClass during code generation. In the UI, tags of implemented interfaces are shown so I was hoping there is a way to get these tags during code generation.
I tried to edit the code generation templates and found macros to get
All interfaces that a class implements: %list="ClassInterface" #separator=", "%
All tags with a given name (of the class that code is being generated for): %classTag:"annotations"%
But unfortunately, I cannot combine these macros, i.e., I cannot pass one interface to the classTag macro so that I can retrieve the tags of that particular interface (and not the one I'm generating code for). Is there a way to get classTags of a specific class / interface?
I also tried to create a separate code generation template and "call" it from the main class code generation template. But inside my template, the classTag macro still only gets the tags of the class.
Thanks to the comments above and especially because of an answer to my question in EA's forum, I was able to setup a little proof of concept achieving what I wanted. I'm answering my question to document my solution in case someone has a similar problem in the future.
After Eve's hint in EA's forum I looked into creating an AddIn for Enterprise Architect to use this AddIn from a code generation template. I started by writing a basic AddIn as explained by #Geert Bellekens in this tutorial. Afterwards I changed the AddIn to fit my needs. This is how I finally got the tagged values (annotations) of the interfaces a class realizes:
First step:
Inside a code generation template, I get all the interfaces a class realizes and pass them to my AddIn:
$interfaces=%list="ClassInterface" #separator=", "%
%EXEC_ADD_IN("MyAddin","getInterfaceTags", $interfaces)%
Second step:
As documented here the repository objects gets passed along with the EXEC_ADD_IN call. I use the repository object and query for all interfaces using the names contained in $interfaces. I can then get the tagged values of each interface element. Simple prototype that achieves this for a single interface:
public Object getInterfaceTags(EA.Repository repo, Object args)
{
String[] interfaceNames = args as String[];
String firstInterfaceName = interfaceNames[0];
EA.Element interfaceElement = repo.GetElementsByQuery("Simple", firstInterfaceName).GetAt(0);
String tag = interfaceElement.TaggedValues.GetAt(0);
return interfaceElement.Name + " has tag value" + tag.Value;
}
I know, there are a couple of shortcomings but this is just a simple proof of concept for an idea that will most likely never be production code.
I'm looking for a way of condensing some of my AS3 code to avoid almost duplicate commands.
The issue is that I have multiple variables with almost the same name e.g. frenchLanguage, englishLanguage, germanLanguage, spanishLanguage
My Controller class contains public static variables (these are accessed across multiple classes) and I need a way to be able to call a few of these variables dynamically. If the variables are in the class you are calling them from you can do this to access them dynamically:
this["spanish"+"Language"]
In AS3 it's not possible to write something like:
Controller.this["spanish"+"Language"]
Is there any way to achieve this? Although everything is working I want to be able to keep my code as minimal as possible.
It is possible to access public static properties of a class this way (assuming the class name is Controller as in your example:
Controller['propertyName']
I'm not sure how this helps to have "minimal code", but this would be a different topic/question, which might need some more details on what you want to achive.
Having said that, I like the approach DodgerThud suggests in the comments of grouping similar values in a (dynamic) Object or Dictonary and give it a proper name.
Keep in mind, that if the string you pass in as the key to the class or dynamic object is created from (textual) user input you should have some checks for the validity of that data, otherwise your programm might crash or expose other fields to the user.
It would make sense to utilize a Dictionary object for a set of variables inherited: it provides a solid logic and it happens to work...
I do not think this is what you are trying to accomplish. I may be wrong.
Classes in AS3 are always wrapped within a package - this is true whether you have compiled from Flash, Flex, Air, or any other...
Don't let Adobe confuse you. This was only done in AS3 to use Java-Based conventions. Regardless, a loosely typed language is often misunderstood, unfortunately. So:
this["SuperObject"]["SubObject"]["ObjectsMethod"][ObjectsMethodsVariable"](args..);
... is technically reliable because the compiler avoids dot notation but at runtime it will collect a lot of unnecessary data to maintain those types of calls.
If efficiency becomes an issue..
Use:
package packages {
import flash.*.*:
class This implements ISpecialInterface {
// Data Objects and Function Model
// for This Class
}
package packages {
import...
class ISpecialInterface extends IEventDispatcher
I saw some extension files which are in TYPO3 4.5. (class.tx_ajaxsearch_pi1.php...), looks like this way:
class tx_ajaxsearch_pi1 extends tslib_pibase {
...
if (defined('TYPO3_MODE') && $TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS']['ext/ajax_search/pi1/class.tx_ajaxsearch_pi1.php']) {
include_once($TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS']['ext/ajax_search/pi1/class.tx_ajaxsearch_pi1.php']);
}
I am checking this document about XCLASS: http://typo3.org/documentation/document-library/core-documentation/doc_core_api/4.1.0/view/3/8/
Questions:
According to this document: http://typo3.org/documentation/document-library/core-documentation/doc_core_api/4.1.0/view/3/8/
Extending TYPO3s PHP classes is recommended mostly for special needs in individual projects. This is due to the limitation that a class can only be extended once. Thus, if many extensions try to extend the same class, only one of them will succeed and in turn the others will not function correctly.
But why class tslib_pibase can be extended many times by different extension classes?
Is it a good habit to put below codes in every extension scripts? Just in case the extension class needs to be extended in the future?
if (defined('TYPO3_MODE') && $TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS']['ext/ajax_search/pi1/class.tx_ajaxsearch_pi1.php']) {
include_once($TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS']['ext/ajax_search/pi1/class.tx_ajaxsearch_pi1.php']);
XCLASS'ing is an approach, when someone substitutes one class with another one. Sounds like inheritance in OOP, but in fact it is different, because you can XCLASS only once, since in TYPO3 global scope one class definition is substituted with another one.
So, i.e. you XCLASS t3lib_db with ux_t3lib_db - that means, taht t3lib_db will never be used in DB processing, but ux_t3lib_db
Sure, your XCLASS can extend the base class, like ux_t3lib_db extends t3lib_db, so it works with inheritance of OOP, but if someone else would like to XCLASS t3lib_db too this will fail simply because TYPO3 will not find t3lib_db in it's scope, because it is already substituted with ux_t3lib_db. So, the only winner will be the one, who XCLASS'ed first.
You can read more here.
But, general note is, that XCLASS'ing is the last option you should try. Use hooks or signals/slots (last works in ExtBase only).
Answering your second question, I can say, that yes, you can do this in 4.5, but no - you shouldn't do that from 6.0.
Hi I am trying to learn JAVA deeply and so I am digging into the JDK source code in the following lines:
URL url = new URL("http://www.google.com");
URLConnection tmpConn = url.openConnection();
I attached the source code and set the breakpoint at the second line and stepped into the code. I can see the code flow is: URL.openConnection() -> sun.net.www.protocol.http.Handler.openConnection()
I have two questions about this
First In URL.openConnection() the code is:
public URLConnection openConnection() throws java.io.IOException {
return handler.openConnection(this);
}
handler is an object of URLStreamHandler, define as blow
transient URLStreamHandler handler;
But URLStreamHandler is a abstract class and method openConnection() is not implement in it so when handler calls this method, it should go to find a subclass who implement this method, right? But there are a lot classes who implement this methods in sun.net.www.protocol (like http.Hanlder, ftp.Handler ) How should the code know which "openConnection" method it should call? In this example, this handler.openConnection() will go into http.Handler and it is correct. (if I set the url as ftp://www.google.com, it will go into ftp.Handler) I cannot understand the mechanism.
second. I have attached the source code so I can step into the JDK and see the variables but for many classes like sun.net.www.protocol.http.Handler, there are not source code in src.zip. I googled this class and there is source code online I can get but why they did not put it (and many other classes) in the src.zip? Where can I find a comprehensive version of source code?
Thanks!
First the easy part:
... I googled this class and there is source code online I can get but why they did not put it (and many other classes) in the src.zip?
Two reasons:
In the old days when the Java code base was proprietary, this was treated as secret-ish ... and not included in the src.zip. When they relicensed Java 6 under the GPL, they didn't bother to change this. (Don't know why. Ask Oracle.)
Because any code in the sun.* tree is officially "an implementation detail subject to change without notice". If they provided the code directly, it helps customers to ignore that advice. That could lead to more friction / bad press when customer code breaks as a result on an unannounced change to sun.* code.
Where can I find a comprehensive version of source code?
You can find it in the OpenJDK 6 / 7 / 8 repositories and associated download bundles:
http://hg.openjdk.java.net/jdk6/jdk6 - http://download.java.net/openjdk/jdk6/
http://hg.openjdk.java.net/jdk7/jdk7 - http://download.java.net/openjdk/jdk7/
http://hg.openjdk.java.net/jdk8/jdk8
Now for the part about "learning Java deeply".
First, I think you are probably going about this learning in a "suboptimal" fashion. Rather than reading the Java class library, I think you should be reading books on java and design patterns and writing code for yourself.
To the specifics:
But URLStreamHandler is a abstract class and method openConnection() is not implement in it so when handler calls this method, it should go to find a subclass who implement this method, right?
At the point that the handler calls than method, it is calling it on an instance of the subclass. So finding the right method is handled by the JVM ... just like any other polymorphic dispatch.
The tricky part is how you got the instance of the sun.net.www.protocol.* handler class. And that happens something like this:
When a URL object is created, it calls getURLStreamHandler(protocol) to obtain a handler instance.
The code for this method looks to see if the handler instance for the protocol already exists and returns that if it does.
Otherwise, it sees if a protocol handler factory exists, and if it does it uses that to create the handler instance. (The protocol handler factory object can be set by an application.)
Otherwise, searches a configurable list of Java packages to find a class whose FQN is package + "." + protocol + "." + "Handler", loads it, and uses reflection to create an instance. (Configuration is via a System property.)
The reference to handler is stored in the URL's handler field, and the URL construction continues.
So, later on, when you call openConnection() on the URL object, the method uses the Handler instance that is specific to the protocol of the URL to create the connection object.
The purpose of this complicated process is to support URL connections for an open-ended set of protocols, to allow applications to provide handlers for new protocols, and to substitute their own handlers for existing protocols, both statically and dynamically. (And the code is more complicated than I've described above because it has to cope with multiple threads.)
This is making use of a number of design patterns (Caches, Adapters, Factory Objects, and so on) together with Java specific stuff such as the system properties and reflection. But if you haven't read about and understood those design patterns, etcetera, you are unlikely to recognize them, and as a result you are likely to find the code totally bamboozling. Hence my advice above: learn the basics first!!
Take a look at URL.java. openConnection uses the URLStreamHandler that was previously set in the URL object itself.
The constructor calls getURLStreamHandler, which generates a class name dynamically and loads, and the instantiates, the appropriate class with the class loader.
But URLStreamHandler is a abstract class and method openConnection()
is not implement in it so when handler calls this method, it should go
to find a subclass who implement this method, right?
It has to be declared or abstract or implemented in URLStreamHandler. If you then give an instance of a class that extends URLStreamHandler with type URLStreamHandler and call the openConnection() method, it will call the one you have overriden in the instance of the class that extends URLStreamHandler if any, if none it will try to call the one in URLStreamHandler if implemented and else it will probably throw an exception or something.
Hi I have a situation where I need to look up the number of recently viewed products on catalog/product/view.phtml. In the recently viewed 'product_viewed.phtml' file it calls
$_products = $this->getRecentlyViewedProducts()
to get the recently viewed. How would I access this method from within the catalog/product/view.phtml file?
I don't know where this method is. I've tried searching for it but it doesn't seem to exist. When I write click it in Netbeans and click go to declaration it takes me to
class Mage_Reports_Block_Product_Viewed extends Mage_Reports_Block_Product_Abstract
Actually on the class itself. This class only has _toHtml(), getCount(), and getPageSize() methods.
I just need to know whether there are any recently viewed products.
Any help most appreciated!
Billy
If you look into 'Mage_Reports_Block_Product_Viewed', you will notice:
$this->setRecentlyViewedProducts($this->getItemsCollection());
That 'getItemsCollection' method is defined in the abstract class... And you will notice this abstract class will create a model based on $_indexName defined in the (subclassed) block.
If you just want the collection, you can probably get away with:
$_products = Mage::getModel('reports/product_index_viewed')->getCollection();
And then adding whatever you want to the collection:
$_products
->addAttributeToSelect('*')
->setAddedAtOrder();
// optionally add other methods similar to Mage_Reports_Block_Product_Abstract::getItemsCollection
Another approach that might be more suited would be to create the original block:
$productViewedBlock = $this->getLayout()->createBlock('reports/product_viewed');
On which you can simply call whatever you want:
$_collection = $productViewedBlock->getItemsCollection();
$_count = $productViewedBlock->getCount();
The getRecentlyViewedProducts function is a magical getter that gets the data that was set with setRecentlyViewedProducts in app/code/core/Mage/Reports/Block/Product/Viewed.php (which builds it using app/code/core/Mage/Reports/Block/Product/Abstract.php's function _getRecentProductsCollection).
This is complicated stuff that you don't want to reproduce; its better, IMO to make your own Block that extends Mage_Catalog_Block_Product_Abstract that will give you access to the same functionality, and drop your new block into the page you're working on.