Simone Tellini » Software Development

Effortless, template-based dynamic tables

Simone — Tue, 31 Jan 2012 19:23:21 +0000

When you develop web applications for a living, sooner or later you’ll need to allow the user to edit collections of data. For instance:

Field 1	Options
	Some option…

To create something like this, I’ve been using a very rough script that simply replicated a hidden template row when required for several years. Eventually, I couldn’t stand its uglyness anymore and I decided to polish it a bit

I’ve based my new script on prototype, thus keeping it short and elegant.

Let’s see the full code required to create the table above:

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Simple, isn’t it?

Here’s what you need to know:

the script automatically sets up all the tables with a dynamicTable class
the template row is automatically hidden
the ID of the table can be repeated as a class together with the addRow class to link the button to the table. If the button is already inside the table, you might just use the addRow class.
the deleteRow class marks the button used to remove its containing row
#{rowId} in the template will be replaced with an unique ID for every row that gets added. You’ll have to use sequential IDs starting from 0 for rows you add before serving the page to the client.

Exploiting prototype Classes, you can subclass DynamicTable and override addRow() or deleteRow() to perform whatever action you need on freshly created rows or when the user removes one.

By the way, you can find the code here.

Quick Sprites: CSS sprites, the easy way

Simone — Sun, 21 Aug 2011 17:02:52 +0000

The use of CSS sprites is a valuable techique for any web developer who wishes to optimize his web site, making it both faster for users and better ranked by search engines.

However, it usually involves more work to pack the images in a single sprite sheet and to update them when the site evolves.

If you never used this technique for this reason, now you won’t have any excuse left: Quick Sprites makes creating and maintaining sprite sheets a breeze

You can see how easy is to work with Quick Sprites in this short video:

Currently available in the Mac App Store.

The Lion, the Witch and the Xcode

Simone — Thu, 21 Jul 2011 20:03:40 +0000

…or maybe it was “The Lion, the Bug and the Xcode“?

Anyway, if you just upgraded your system to Lion, then downloaded the new Xcode from the App Store, tried to run it just to get welcomed by a sparkling crash along the lines of

UNCAUGHT EXCEPTION (NSInternalInconsistencyException): Couldn’t load plug-in ‘com.apple.dt.IDE.IDEiPhoneSupport’ while firing fault for extension ‘Xcode.Device.iPhoneSimulator’

Don’t panic!

Simply go to your Applications folder and re-run the Xcode installer. The second time it’ll get it right, or at least it did for me.

Using SQLi Import with Oracle

Simone — Thu, 09 Dec 2010 11:33:38 +0000

SQLi Import is a nice eZ Publish extension that allows you to develop data importers in a quick and elegant way.

Sadly, it comes only with MySQL support, but it takes only a minute to make it work with Oracle too. So here’s the SQL code I’ve used to make it happy

(tested with SQLi Import 1.2.0 and eZ Publish 4.4)

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CREATE TABLE sqliimport_scheduled (
id INT NOT NULL,
handler VARCHAR(50),
label VARCHAR(255),
options_serialized CLOB,
frequency VARCHAR(30) NOT NULL,
NEXT INT DEFAULT 0,
user_id INT,
requested_time INT,
is_active SMALLINT DEFAULT 0,
manual_frequency INT DEFAULT 0,
PRIMARY KEY (id)
);

CREATE TABLE sqliimport_item (
id INT NOT NULL,
handler VARCHAR(50),
options_serialized CLOB,
user_id INT,
requested_time INT DEFAULT 0,
STATUS SMALLINT DEFAULT 0,
percentage_int SMALLINT DEFAULT 0,
TYPE SMALLINT DEFAULT 1,
progression_notes CLOB,
process_time INT DEFAULT 0,
scheduled_id INT,
PRIMARY KEY (id)
);

CREATE SEQUENCE se_sqliimport_item;
CREATE SEQUENCE se_sqliimport_scheduled;

CREATE OR REPLACE TRIGGER tr_sqliimport_scheduled_id
BEFORE INSERT ON sqliimport_scheduled
FOR EACH ROW
WHEN ( NEW.ID IS NULL )
BEGIN
SELECT se_sqliimport_scheduled.NEXTVAL
INTO :NEW.ID
FROM dual;
END;
/

CREATE OR REPLACE TRIGGER tr_sqliimport_item_id
BEFORE INSERT ON sqliimport_item
FOR EACH ROW
WHEN ( NEW.ID IS NULL )
BEGIN
SELECT se_sqliimport_item.NEXTVAL
INTO :NEW.ID
FROM dual;
END;
/

I do hate MySQL

Simone — Fri, 12 Jun 2009 08:25:43 +0000

I can’t stand it, really.

I’m using it at the moment only because I’m forced to. I can’t help considering it as a toy DB, especially comparing it to PostgreSQL or SQL Server or any other serious RDBMS.

The last thing that hit my nerve is this bug. Come on… can’t it even handle foreign keys in a decent way?

And I’m trying not to think that it allows you to define a table with foreign keys and silently ignore them.

FeedbackReporter and Mantis integration

Simone — Sat, 02 May 2009 12:23:30 +0000

I’ve just written a small script to store reports generated by FeedbackReporter on a Mantis system.

It should come handy to keep track of your application crashes (crash? uh? My apps never crash! )

You can download it here.

Simply extract it on your webserver and edit config.php to adjust your settings.

It can work in two ways: if you’re installing it on the same server running mantis, set MANTIS_LOCAL to true and MANTIS_PATH to the root of your mantis installation.

Otherwise, you can even install it on a different server and let it communicate with your mantis via SOAP. In order to do this, set MANTIS_LOCAL to false and edit MANTIS_URL. This setup needs the SOAP extension of PHP5, so make sure it’s available.

Feedback is welcome, of course.

Connection without a listening socket?

Simone — Tue, 10 Feb 2009 11:25:00 +0000

I’ve encountered a network problem that left me a bit puzzled.

Usually, when you want to setup a TCP connection between two sockets (let’s called them S1 and S2), you need to perform these steps on the server:

create S1
bind S1 to a port (or to a port/address, if you need to)
set S1 to listen for connections

on the client:

create S2
tell S2 to connect to S1

and finally, the server receives the connection attempt and accepts it to remove it from the backlog of the listening socket.

Well, apparently there’s another way, which I suspect few know about.

Check out this simple application:

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using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace SocketTest
{
class Program
{
private static IPEndPoint a = new IPEndPoint( IPAddress.Loopback, 18000 );
private static IPEndPoint b = new IPEndPoint( IPAddress.Loopback, 18001 );

static void Main(string[] args)
{
Thread threadA = new Thread( ThreadA );
Thread threadB = new Thread( ThreadB );

threadB.Start();
threadA.Start();
}

static void ThreadA()
{
for(;;) {
try {
Socket sock = new Socket( a.AddressFamily, SocketType.Stream, ProtocolType.Tcp );

sock.Bind( b );
sock.Connect( a );

Console.WriteLine( "Connected from " + b + " to " + a );

Thread.Sleep( Timeout.Infinite );
}
catch {
}
}
}

static void ThreadB()
{
for(;;) {
try {
Socket sock = new Socket( b.AddressFamily, SocketType.Stream, ProtocolType.Tcp );

sock.Bind( a );
sock.Connect( b );

Console.WriteLine( "Connected from " + a + " to " + b );

Thread.Sleep( Timeout.Infinite );
}
catch {
}
}
}
}
}

Let’s see what happens compiling and running it:

Yes, you get a connection between the two sockets. It’s something I was never told about and I would have never expected to see. But it’s correct as per RFC 793.

I’ve found out about it when a couple of clients on a test system started connecting between themselves, while they were supposed to connect to 2 different servers on localhost. Both clients were periodically trying to connect to their server, which was down. They were creating a new socket for every attempt, without binding it, thus Windows’ TCP/IP stack assigned a sequential port number to them. Eventually, the two processes reached the configuration required for the “Simultaneous Connection Synchronization” as described in the RFC.

Interesting. I guess you live and you learn.

Quote of the Day

Simone — Mon, 04 Aug 2008 20:53:09 +0000

[...] a good programmer cultivates the virtue of laziness. (But not just any laziness: you must be aggressively, proactively lazy!)

– Chris Pine, dealing with the DRY rule

Quote of the Day

Simone — Sat, 12 Jul 2008 10:15:14 +0000

Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.

– Richard Cook, read on FSM

Quote of the Day

Simone — Sun, 06 Jul 2008 19:21:04 +0000

[...] as we all know, premature optimization is the root of all evil.

– from a cocoa-dev email

amen!