Freya.no » Dev

Flex: force focus on parent change

Tatyana — Sat, 24 Jul 2010 08:36:05 +0000

I was trying to solve a problem of resetting a focus if the parent changes. I had different buttons that show the same .mxml-form but with different data. The problem was that I needed the focus to be on the first date-field whenever the form is shown so that the user can begin typing data right away.

So for each time one of the buttons is pushed I need the focus to be on myDate-field. To solve the problem I used “updateComplete“-property of the field.

DataForm.mxml

Recipe for a high-quality “equals” method

Tatyana — Sat, 17 Apr 2010 21:49:25 +0000

1. Use the == to check if the argument is a reference to this object.

2. Use the instanceof operator to check if the argument has the correct type.

3. Cast the argument to the correct type.

4. For each “significant” field in the class, check if that field of the argument matches the corresponding field of this object.

5. Always override hashCode when you override equals.

6. Don’t substitute another type for Object in the equals declaration.

7. Write unit-test.

@Override
public boolean equals(Object obj) {
   if(obj == this) {
      return true;
   }

   if(!(obj instanceof Person)) {
      return false;
   }

   Person p = (Person)obj;

   return p.name.equals(name) &&
            p.birthday.equals(birthday) &&
            p.personNumber == personNumber;
}

Ref.”Effective Java” by Joshua Bloch

EJB 3.0 Roles

Tatyana — Thu, 04 Mar 2010 19:14:18 +0000

I had some difficult time understanding all the roles regarding EJB3. Here is an easy-to-remember description of these roles that I found here.

Imagine a factory producing computers:

Bean Provider:
Chip manufacturer. On the chip, there will be a label with “Warranty void if removed” the chip has the logic and the label sets a Role. If you are not authorized to repair it, warranty voids. (i.e. you cannot access the internal chip if you are not in the role of “Warranty Repair Person”.)

Application Assembler
Mainboard assembler. It takes various chips and puts them on the mainboard. If any additional resistor or cable are required, it will put everything togheter to have something that is some kind of working unit but requires additional assembling.

EJB Server Provider
The EJB Server provider is the Computer Case manufacturer providing a case with a power supply. Is a container for the mainboard

Deployer
As every computer case is different and power voltage vary country by country, the Deployer makes sure to adapt the mainboard to the working environment. In this case adjusts the Voltage on the power supply, and connects the cables. At the same time he will define who are the person allowed to repair it (i.e. provide a list of authorized repair centers)

Persistence Provider
the persistence provider could be the network card company that provides the driver to connect to a network.

System Administrator
Is the person in charge to install the operating system and do necessary configuration changes to the OS to connect to the server, and will make sure to monitor that everything is working fine.

More about Enterprise Java Beans 3.0 and Sun Certified Business Component Developer (SCBCD) certification here.

Clean code

Tatyana — Thu, 25 Feb 2010 20:13:49 +0000

The book by Robert C. Martin “Clean Code” is a really very useful material for all programmers. You can disagree with him sometimes (as I do), but it still provides some useful notes that helped me to place my programmer experience and knowledge where they belong. Here I’ll provide some key notes that I did while reading the book and that I’d like to memorize.

What you as a programmer SHOULD DO:

1. Give everything meaningful, searchable and pronounceable names.
2. Use names that other programmers can understand. Remember that the code is for programmers, not customers.
3. Functions should be small and smaller than that.
4. Functions should do one thing. They should do it well. They should do it only.
5. The ideal number of arguments for a function is zero. Max 3.
6. Prefer exceptions to returning error codes. Create informative error messages.
7. Prefer meaningful names to comments.
8. Write JavaDoc only for public API’s.
9. Format your code. While working in a team use a single formatting style.
10. Test your code with clean tests. Remember that test code is just as important as production code.
11. Test just one concept per test.
12. Test should follow the FIRST rule:

Fast

Independent

Repeatable

Self-validating

Timely

What you as a programmer should AVOID:
1. Avoid encoding
2. Avoid duplicate code. Watch out not only duplicate functions but also duplicate functionality.
3. Avoid noisy, redundant, uninformative comments. Remember that one of the more common motivations for writing comments is bad code.

Java conversions and 7 Golden rules of widening, boxing & varargs

Tatyana — Tue, 16 Feb 2010 19:31:43 +0000

Here is a very useful java conversion table that I’ve created while preparing for the Sun Certified Java Programmer exam.

Java primitive conversions table

And here is a complete overview of the Golden rules of widening, boxing & varargs:

1. Primitive Widening > Boxing > Varargs.
2. Widening and Boxing (WB) not allowed.
3. Boxing and Widening (BW) allowed.
4. While overloading Widening + vararg and boxing + vararg are mutually exclusive of each other.
5. Widening between wrapper classes not allowed
6. Widening+varArgs & Boxing+varargs are individually allowed (but not allowed in overloaded version of method)
7. Boxing+Widening is preferred over Boxing+Varargs.

More explanation here.

Building opensource Qt on Windows

kent — Sun, 20 Dec 2009 10:43:47 +0000

Open Visual Studio command prompt.

Go to the folder you installed the source files in.

Execute configure with the wanted options.

S:\Qt\2009.04\qt>configure -debug-and-release -fast -no-webkit -opensource

This is the Qt for Windows Open Source Edition.

You are licensed to use this software under the terms of
the GNU General Public License (GPL) version 3
or the GNU Lesser General Public License (LGPL) version 2.1.

Type '3' to view the GNU General Public License version 3 (GPLv3).
Type 'L' to view the Lesser GNU General Public License version 2.1 (LGPLv2.1).
Type 'y' to accept this license offer.
Type 'n' to decline this license offer.

Do you accept the terms of the license?

Wait.

Then execute nmake and wait.

“configure” command line options

Usage: configure [-buildkey ]
 [-release] [-debug] [-debug-and-release] [-shared] [-static]
 [-no-fast] [-fast] [-no-exceptions] [-exceptions]
 [-no-accessibility] [-accessibility] [-no-rtti] [-rtti]
 [-no-stl] [-stl] [-no-sql-] [-qt-sql-]
 [-plugin-sql-] [-system-sqlite] [-arch ]
 [-D ] [-I ] [-L ]
 [-help] [-no-dsp] [-dsp] [-no-vcproj] [-vcproj]
 [-no-qmake] [-qmake] [-dont-process] [-process]
 [-no-style-