Mac OS X Leopard - ARCAism

All controls come in three standard sizes: regular, small, and mini. Although you can manually
change the size of a control and its contents, using one of the predefined sizes ensures that
your controls will always match the rest of the system, regardless of design changes down the
road. In general, Apple’s Human Interface Guidelines suggest using regular controls whenever
possible, reserving the use of the smaller controls for when space is at a premium.
NOTE Did you think the Mac’s usability was an accident? Far from it, every pixel has been
sweated over by design experts and explained in excruciating detail in Apple’s Human Interface
Guidelines. These are required reading for any Mac developer, and also interesting for
any user who’d like to get to know more about what makes using a Mac such a great experience.
The guidelines, usually referred to as the HIG (rhymes with dig), are available in Xcode’s
documentation and online.
Figure 25-10. Changing Autosizing
attributes in the Inspector
Moving down to the View Size subsection, you can
set size and location based on any corner or edge, or the
view’s center. You can also align and center multiple
views. What you really want is to change the autosizing
behavior, as shown in Figure 25-10.
On the left side of the Autosizing section is a
schematic representation of your view inside its superview.
The inner rectangle represents your view. The
vertical and horizontal arrows inside your view represent
which direction you want your view to resize in.
The struts connecting your view to the superview represent
which sides of your view you want to be fixed in
relation to the superview. The expected results of the settings
are animated on the right.
By clicking the resize directions and struts in the
schematic, you can change the effects shown in the animation.
A little experimentation shows that removing
all the struts will enable your text area to remain centered. Save and run the interface to verify
that this is so.
Bindings
CHAPTER 25 MAC OS X DEVELOPMENT: THE TOOLS 461
As you’ve seen, even simple controls like the text field have a lot of attributes. Some of these
attributes are displayed to the user, such as the title. Other attributes affect the control itself, such
as its size, or whether it’s hidden. While you can set an initial state during the design of your
interface, some attributes may need to change at runtime.
Traditionally, getting and setting a control’s value was accomplished via an intermediary
object, called a controller. A programmer would write glue code in the controller to perform the
actual getting and setting of values.
Cocoa’s bindings feature eliminates the need for this glue code by letting controls bind their
values to other objects. For example, check boxes on a preference panel might be bound to the
user defaults system. The value of a date field might be bound to the value of a date picker. Or, a
user-editable value might be bound to a key in the document controller. Unlike traditional glue
code, a bound value is always kept in sync automatically.
The Inspector’s Bindings tab contains a list of bindable attributes. Within each binding, you
can set the object, the key name, and several options. You can also set a value transformer to
automatically convert between value types. For example, an object might have a URL attribute
that you want to bind to another object’s path attribute. Since URLs have their own class, NSURL,
and paths are instances of the NSString class, you wouldn’t be able to bind a URL to a path without
the assistance of a value transformer.