Pioneering Software

CSV is a ubiquitous importing and exporting format for tables of information conforming to row-column layout. Lines correspond to rows. On each line, commas separate values under each column; hence Comma-Separated Values. Values between commas define table-cell contents, strings or numbers. The format is relatively flexible, relatively easy for machines and even humans to read and write.

In terms of user stories, it answers the following requirement.

As a: database maintainer

I want to: import information from external files, particularly Comma-Separated Value files where rows appear on each line and columns within each row have comma delimiters

So that I can: select columns (and rows) from the CSV files and merge these to create other new pieces of information.

Question is, How do you import CSV files in Rails 3. This article attempts an answer, or at least part of an answer, enough perhaps to point you in the right direction. You can find the sources here at GitHub.

C++ and Objective-C do not always mix too well, although the two languages are fully compatible.

With respect to compilation phases, alternating between C, C++, Objective-C and Objective-C++ presents no problem. You just write your software accordingly, freely mixing C, Objective-C, C++ and Objective-C++. Just make sure that the compiler knows what each translation unit contains, normally by source file extension: c for C; cc or cpp or cxx for C++; m for Objective-C; and mm for Objective-C++.

That being specified correctly, your sources compile and link without issues. Only when you start running the code side-by-side however, you might find that memory management can become something of a mishmash. Basic C++ fundamentally has no memory management; I mean nothing automatic. Asking for memory when you want it, freeing memory when you’re done with it: that is all bare C++ gives you. So you typically just roll your own, or find some more-advanced alternative such as Boehm’s garbage collector.

Wouldn’t it be nice however, if you could just simply retain, release and auto-release your C++ objects, just like you do with NSObjects? It would be very nice.

This article outlines a little “trick” for retaining C++ objects on Mac and iPhone. It takes advantage of C++ inheritance; and is simple, so no dependence on internals of CFTypeRef or NSObject. The memory cost is low; just one additional NSObject-derived object per retained C++ object. Final feature, implementation separates from interface by design. Hence you can include retaining within bodies of source without the things being retained having any knowledge of Objective-C. Translation units remain plain old C++, no additional dependencies. The implementation exists apart.

MIT-licensed code provided in full.

Ole Begemann has done some very useful work, porting the gloss-caustic shader to iPhone OS. This work has been long overdue. Many thanks Ole!

I’ve merged Ole’s changes into my Git repo, albeit with a few modifications. This article outlines the changes to the changes.

Matt Gallagher recently wrote a very useful article about drawing gloss gradients using Core Graphics. In his article, Matt describes how to reproduce the oft-seen glossy gradient effect. Thanks Matt! It’s a nice article. “Cocoa with Love” lovingly provides the working source code. This little article aims to complement Matt’s work.

I’ve also re-factored the software and packaged the result within an Objective-C class called RRGlossCausticShader. This packaging automatically adds support for key-value coding and observing. Bindings then let you easily wrap the class within a little application able to adjust the many parameters interactively.

This is the scenario: your user interface comprises an outline view and a hierarchical data model. You want the outline view to display the hierarchy and remember the expansion state automatically in preferences. Hence when the user re-runs the application, the items that were expanded are still expanded, and vice versa: what was collapsed remains so. Outline view, tree controller, hierarchical model, bindings. That’s the recipe.

According to some, storing expansion state of an outline view when used with a tree controller is not just difficult: it’s impossible! But is it? No, is the simple answer. It’s actually quite easy. In this article I introduce a new helper class called RROutlineViewExpandedItemsAutosaver! Original aren’t I? It does not involve sub-classing or access to private methods. The solution presented uses only documented interfaces and only requires a small stateless class instance for handling all outline view auto-saving technicalities. It does assume Core Data use for modelling. But you can easily adapt the technique for other data-model implementations.

The last article on this subject (Organising view controllers) started looking at an example. Apple’s ViewController sample illustrates basic use of multiple view controllers. This article completes the work.

Download the source if you would rather skip ahead. Sometimes it’s easier that way. You can see the code in its full context. Snippets and extracts don’t always tell you everything you need to know.

Understanding how individual view controllers work is one thing. Organising them is another. Applications typically deal with multiple view controllers. Views can change dynamically. Hence view controllers need dynamic capabilities.

This article presents an idea for organising view controllers within an application. Design goals include: flexibility, simplicity, convention over configuration.

NSViewController. It’s an enigmatic class.

Exactly what is it? When should it be used? Apple’s documentation does not paint a clear picture. What is there to glean from its interface, implementation as well as others’ work on this subject?

Permutations! I’ve hit this issue quite a number of times in my life: at university, at work. It’s not unusual to encounter problems where it’s very handy to able to iterate all possible permutations of something. And catch is: standard libraries sometimes do not offer any help. The engineer is left to tackle the problem by him- or herself.

Factorial, denoted by n! and defined as the product of all positive integers less than or equal to n.