To give some feedback to the user I want to include a display of the number of images that will be exported. I can do that by using bindings: by binding text on the window to an ivar in my Random_Wok object.

I create an ivar called imagesToProcess and an accessor to set it:

In -willBeActivated, I add some code to set it up before it is used:

And since changes in the image type (master or version) can change the number of images, I have to set it each time the export type changes:

That is all the code except for this method:

It returns "s" if imagesToProcess is more than one, otherwise an empty string. I need that in order to implement correct pluralization of my display string.

To display the image count on the window I add an NSTextField in the corner like this:

Its value is unimportant because I will be constructing it dynamically with bindings, but it helps to have a descriptive string there. I set up its bindings like this:

The Display Pattern string is what does the magic. Value1 and Value2 are bound to different key paths. The first to the value given by imagesToProcess, and the second to the plural string given by pluralImagesToProcess:

When these are substituted into the Display Pattern string, the result is what the user needs to see how many images are selected:


Because I implemented the accessors and I use them to change the value, bindings take care of doing this display updates automatically. If I select images in Aperture that include some with multiple versions of one master, the image count displayed changes when I click Master and then Version, just as it should.

The other parts of this series can be found via the Cocoa page.

Tags: Aperture, Plug-ins, Cocoa, Random Wok, Bindings