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Showing posts from July, 2011

Avoid Fetch-Object Abuse

Lately I'm finding a lot of instances of the mysql_fetch_object() function being used in a particular codebase I help maintain. Unfortunately, I've yet to see it used correctly. It always seems to be used to retrieve a stdClass object from a query result where mysql_fetch_array() or mysql_fetch_assoc() would be the more appropriate choice.
$row = mysql_fetch_object($result); $kitten = new Kitten(); $kitten->setName($row->name); $kitten->setColor($row->color); ... Put aside the argument that the code should be using PDO or the MySQLi extension instead of the legacy MySQL extension. mysqli_result::fetch_object() and PDOStatement::fetchObject() have the same potential for abuse. The above code is wrong because the returned result is an object but treated like it's an array.

The mysql_fetch_array() and mysql_fetch_assoc() functions are used to retrieve a row from the query's result set. I prefer to use mysql_fetch_assoc() so I can access the values using column…

Smalltalk Challenge: Post 10 - Conclusions

So here I am, more than 20 hours with Smalltalk and 10 blog posts about my experiences as required by the terms of my challenge. Josh said he chose Smalltalk for me because of the language's history of helping giving rise to object-oriented programming, which he thinks I hate. (For the record I don't hate OO; I hate the awkwardness and complexity its over-zealous application inflicts.) But I think secretly he was hoping it would endear me to Java in the same way as I was hoping OCaml would help him see past Java. Smalltalk gave me a newfound respect, not for OO, but for the language's innovations and lasting influence. If anything in relation to current-day OO practices, my experience confirmed how botched OO adoption has been given what it was intended to be. Regardless, while I don't think I'll be using Smalltalk in the foreseeable future, it was definitely fun to explore and gave me a lot of things to think about.

Smalltalk isn't a popular "mainstream&q…

Smalltalk Challenge: Post 9 - Koans

Besides tinkering with turtles and hashes in Squeak, I secretly went back to GNU Smalltalk and went through some of the Smalltalk Koans. Sssh... don't tell Josh!

Programming koans are a series of failing unit tests that a student reads through and corrects. Each test demonstrates a particular concept in the language. They can be a fun way to review one's understanding of a language, and occasionally learn something new. Here's an of a koan:
testSingleCharacterFromString [ | string | string := 'Smalltalk'. self expect: (self fillMeIn) toEqual: (string at: 1). self expect: (self fillMeIn) toEqual: (string at: 6). ]When the test suite is run, it displays:
Do not lose hope. Expected value should equal actual value. Expected : FILL ME IN Actual : $S (an instance of Character) TestString#testSingleCharacterFromString has damaged your karma (in src/koans/ name of the method indicates it is possible access the characters that make up …

Smalltalk Challenge: Post 8 - Virtual Images

Virtualization is in vogue right now as companies use such technology to run multiple systems on consolidated hardware. Remember, Smalltalk was designed as a language and an environment. No one is about to replace Windows (or Ubuntu, though I'm tempted) with Smalltalk as their operating system, so it makes sense for it to be implemented as a virtual machine.

Similar to products like VMWare Workstation or VirtualBox, most Smalltalk implementations consist of a Virtual machine (VM) application and an image file. The image file contains the definition and state of the Smalltalk environment which is realized by the VM. It may be helpful to think about the image file as a program saved somewhere on your computer's hard drive, and the VM is your computer's processor that executes the code to do something useful.

A Squeak installation consists of four files: a VM executable and three files that make up the image.
The VM is the interpretor that "runs" a Smalltalk image.Th…

Smalltalk Challenge: Post 7 - Turtles Ahoy!

I can remember going down to the computer lab while in grade school and using Logo on the then state-of-the-art Apple IIe computers. Supposedly Logo allowed students to explore mathematics in a tangible way, but I don't remember doing much more than drawing shapes by moving the little "turtle" around on the green screen and I still don't have much confidence in my math skills 20 years later. I don't think Logo helped kindle my interest in computers, either; games like The Oregon Trail and Where in the World is Carmen Sandiego and the Commodore 64 computer were far more influential to me. But drawing little green triangles and squares was fun. And while Logo may not have been as influential in my education as Papert would have hoped, it was extremely influential to Smalltalk. In fact, the graphics Pen object is actually very similar to Logo's turtle.The Pen class is used for drawing. It inherits from BitBlt which allows it to perform raster drawing on any form…