I often see people use the keyword using in their Haxe code. It seem to go after the import statements.
For example, I found this is a code snippet:
import haxe.macro.Context;
import haxe.macro.Expr;
import haxe.macro.Type;
using haxe.macro.Tools;
using Lambda;
What does it do and how does it work?
The "using" mixin feature of Haxe is also referred as "static extension". It's a great syntactic sugar feature of Haxe; they can have a positive effect on code readability.
A static extension allows pseudo-extending existing types without modifying their source. In Haxe this is achieved by declaring a static method with a first argument of the extending type and then bringing the defining class into context through the using keyword.
Take a look at this example:
using Test.StringUtil;
class Test {
static public function main() {
// now possible with because of the `using`
trace("Haxe is great".getWordCount());
// otherwise you had to type
// trace(StringUtil.getWordCount("Haxe is great"));
}
}
class StringUtil {
public static inline function getWordCount(value:String) {
return value.split(" ").length;
}
}
Run this example here: http://try.haxe.org/#C96B7
More in the Haxe Documentation:
Haxe static extensions in the Haxe Manual
Haxe static extensions tagged articles in the Haxe Code Cookbook
Currently I'm experimenting and learning the Dart language.
I'm creating an abstract class with two abstract methods called IAnimal like this:
abstract class IAnimal
{
String Walk(int distance);
String Eat(String food);
}
Next I create a Dog class that should implement the 2 methods.
class Dog implements IAnimal
{
Dog(String name) {
this._name = name;
}
String _name;
}
But the dart analyser does complain about the 2 missing methods, is this intended behaviour or not supported?
This should indeed give a warning, the Dart Analyzer from the command line does the trick. This was an issue with WebStorm and Sublime Text not triggering the Dart Analyzer.
Here it shows a warning DartPad maybe the analyzer doesn't run or isn't finished yet.
I'm trying to learn how to implement logging using the examples/tutorial in:
http://blog.dartwatch.com/2013/05/campaign-to-use-real-logging-instead-of.html#comment-form
But having imported the libraries this line in main will not compile because the class 'PrintHandler' is not recognized and Google has not been a help in this case. My server application consists of a main and three classes. I'm new at Dart. Below I've extracted the logging code that I added.
In what library is 'PrintHandler'? Is this a class I need to write?
library server;
import 'package:logging_handlers/logging_handlers_shared.dart';
import 'package:logging/logging.dart';
final _serverLogger = new Logger("server"); // top level logger
void main() {
Logger.root.onRecord.listen(new PrintHandler()); // default PrintHandler
_serverLogger.fine("Server created");
}
class A {
}
class B {
}
class C {
}
It looks like the class was changed to LogPrintHandler but the tutorial and documentation were not updated.
Is there a way to do something akin to import <BLAH> as in actionscript? I've got some classes that I don't want to type the full class name out for every time I use them. That's why I'm trying to find an import as, or var C = ImportedClassThatIDontWantToTypeEveryTime. I've tried a few different ways, such as:
package com.mysite.blah {
// doesn't work
import com.mysite.ImportedClassThatIDontWantToTypeEveryTime as C;
// also doesn't work
import com.mysite.ImportedClassThatIDontWantToTypeEveryTime;
var C:Class = ImportedClassThatIDontWantToTypeEveryTime;
// ????
public class SomeOtherClass {
public function blah():void {
C.doSomething();
}
}
}
I know there is a way to do this - I've done it before years ago. However, I can't remember how to do it. Help?
What IDE are you using? I ask this because I haven't had to type out a class-path in full in years. The auto-complete features of both FlashDevelop and FlashBuilder will allow you to type the first couple of letters of the class you want in place, select it from a list, and it will automatically add the appropriate import statement to the top of your class.
I've tried to use the new Groovy Grape capability in Groovy 1.6-beta-2 but I get an error message;
unable to resolve class com.jidesoft.swing.JideSplitButton
from the Groovy Console (/opt/groovy/groovy-1.6-beta-2/bin/groovyConsole) when running the stock example;
import com.jidesoft.swing.JideSplitButton
#Grab(group='com.jidesoft', module='jide-oss', version='[2.2.1,)')
public class TestClassAnnotation {
public static String testMethod () {
return JideSplitButton.class.name
}
}
I even tried running the grape command line tool to ensure the library is imported. Like this;
$ /opt/groovy/groovy-1.6-beta-2/bin/grape install com.jidesoft jide-oss
which does install the library just fine. How do I get the code to run/compile correctly from the groovyConsole?
There is still some kinks in working out the startup/kill switch routine. For Beta-2 do this in it's own script first:
groovy.grape.Grape.initGrape()
Another issue you will run into deals with the joys of using an unbounded upper range. Jide-oss from 2.3.0 onward has been compiling their code to Java 6 bytecodes, so you will need to either run the console in Java 6 (which is what you would want to do for Swing anyway) or set an upper limit on the ranges, like so
import com.jidesoft.swing.JideSplitButton
#Grab(group='com.jidesoft', module='jide-oss', version='[2.2.1,2.3.0)')
public class TestClassAnnotation {
public static String testMethod () {
return JideSplitButton.class.name
}
}
new TestClassAnnotation().testMethod()
I finally got it working for Groovy Shell (1.6.5, JVM: 1.6.0_13). This should be documented better.
First at the command line...
grape install org.codehaus.groovy.modules.http-builder http-builder 0.5.0-RC2
Then in groovysh...
groovy:000> import groovy.grape.Grape
groovy:000> Grape.grab(group:'org.codehaus.groovy.modules.http-builder', module:'http-builder', version:'0.5.0-RC2')
groovy:000> def http= new groovyx.net.http.HTTPBuilder('http://rovio')
===> groovyx.net.http.HTTPBuilder#91520
The #grab is better used in a file than the shell.
Ok. Seems like this a short working demo (running from the groovyConsole)
groovy.grape.Grape.initGrape()
#Grab(group='com.jidesoft', module='jide-oss', version='[2.2.1,2.3.0)')
public class UsedToExposeAnnotationToComplier {}
com.jidesoft.swing.JideSplitButton.class.name
When run it produces
Result: "com.jidesoft.swing.JideSplitButton"
Very cool!!
The import statement must appear after the grabs.
Ps. At least one import statement must exists after the grabs
#Grab(group='com.jidesoft', module='jide-oss', version='[2.2.1,)')
import com.jidesoft.swing.JideSplitButton
public class TestClassAnnotation {
public static String testMethod () {
return JideSplitButton.class.name
}
}
Different example using latest RC-2 (note: Grab annotates createEmptyInts):
// create and use a primitive array
import org.apache.commons.collections.primitives.ArrayIntList
#Grab(group='commons-primitives', module='commons-primitives', version='1.0')
def createEmptyInts() { new ArrayIntList() }
def ints = createEmptyInts()
ints.add(0, 42)
assert ints.size() == 1
assert ints.get(0) == 42
Another example (note: Grab annotates getHtml):
// find the PDF links in the Java 1.5.0 documentation
#Grab(group='org.ccil.cowan.tagsoup', module='tagsoup', version='0.9.7')
def getHtml() {
def parser = new XmlParser(new org.ccil.cowan.tagsoup.Parser())
parser.parse("http://java.sun.com/j2se/1.5.0/download-pdf.html")
}
html.body.'**'.a.#href.grep(~/.*\.pdf/).each{ println it }
Another example (note: Grab annotates getFruit):
// Google Collections example
import com.google.common.collect.HashBiMap
#Grab(group='com.google.code.google-collections', module='google-collect', version='snapshot-20080530')
def getFruit() { [grape:'purple', lemon:'yellow', orange:'orange'] as HashBiMap }
assert fruit.inverse().yellow == 'lemon'