Re: NSProgressIndicator and some very basic stuff ...

FROM : Mike Abdullah
DATE : Mon May 19 23:27:00 2008

On 19 May 2008, at 20:58, John Love wrote:

> I am having some basic problems getting an indeterminate 
> NSProgressIndicator
> (INSPI) to spin.  Since I have just recently started to learn XCODE 
> and
> Cocoa, I began with "Learning Cocoa and Objective C".  I have also 
> printed
> out much of Apple's docs, e.g., on the INSPI.  I just finished 
> developing an
> app in AppleScript Studio, so I am very familiar with XCODE and IB. 
> Plus, a
> long time ago, I delved into C++ ... so that helps ... and I have 
> poured
> over the concepts of outlets and actions and how to connect 
> everything in IB
> ... but something is just not working right.  So, I decided to go 
> from the
> beginning and describe everything to you so you can tell me where "I 
> parked
> my brain".
>
> I have developed a multi-document Cocoa app whose nib contains the 
> usual
> stuff plus a Window and an NSObject, 
> "CalculationIndicatorController" (CIC),
> whose class has the same name.  The Window has an INSPI, whose class 
> is
> CIC.


This all be a bit crazy. There's almost certainly NO need for you to 
subclass NSProgressIndicator ever, especially in this case.

> Within IB, the CIC has one outlet = "itsWindow" and one action =
> "spin:".  In general, I must be doing something right, because in each
> window, via CMD-N, I have a Toolbar showing ... the INSPI is just 
> giving me
> fits for now.
>
> // CIC.h looks like:
>
> #import <Cocoa/Cocoa.h>
>
> @interface CIC:NSProgressIndicator {
>    IBOutlet NSWindow *itsWindow;
> }
>
> - (IBAction) spin:(NSWindow *)sender on:(BOOL)start;
> @end
>
> =====
>
> // CIC.m looks like:
>
> #import "CIC.h"
>
> @implementation CIC
>
> - (id) init {
>    if (self = [super init]) {
>        [self setUsesThreadedAnimation:YES];
>    }
>
>    return self;
> }
>
>
> - (void) awakeFromNib {
>    itsWindow = [self window];
>    [self spin:itsWindow on:TRUE];
> }
>
>
> - (IBAction) spin:(NSWindow *)sender on:(BOOL)start; {
>    if (start)  [self startAnimation:sender];
>    else        [self stopAnimation:sender];
> }
>
>
> Now ... back to IB:
>
> 1) When I control-drag from the INSPI (the "lock washer") in the 
> window to
> the window's title bar, I select outlet = "itsWindow" .. so far, so 
> good ..
> but when I control-drag from the CIC in the nib window to the 
> window's title
> bar, I see TWO outlets = "itsWindow" .. so confusion #1 ??
>
> 2) Now, there is clearly an Action labelled "IBAction" in the source 
> code
> and there is an Action in the Class Actions pane of IB when I have 
> selected
> the CIC in the nib window.  As an aside, the Outlet appeared 
> automatically
> once I placed the IBOutlet in the source code .. however, even 
> though the
> IBAction was also in the source code, I had to manually add the 
> Action =
> "spin:" within IB .. so confusion #2 ??


You've used (IBAction) but the actual method itself is not a valid 
action message. Actions MUST take the form:

- (IBAction)doSomething:(id)sender

where sender is an object of some kind. You can even do this if you 
really wanted to but it's slightly pointless:

- (IBAction)doSomething:(MyClass *)sender

Either way it doesn't matter, because you don't need to be doing all 
this subclassing.
>
>
> 3) So, just like I did in Apple's Currency Converter Project (whose 
> source
> for the control-drag was a Button), I control-drag from the window's 
> title
> bar to the INSPI (the "lock washer") in this window - based on the
> assumption that the sender is the NSWindow (???).  I expected to be 
> greeted
> with having to select the Action = "spin:" .. but all I saw was the 
> choice
> of outlets = "delegate" and "initialFirstResponder".  The same thing
> occurred when I control-drag from the window's title bar to the CIC 
> in the
> nib window.  Just for the record, I did select 
> "initialFirstResponder" ..
> but where is the Action selection = "spin:" .. confusion #3 ??
>
> My MainDocument.m file has a *- (void)
> windowControllerDidLoadNib:(NSWindowController*)aController* method 
> which
> sets up everything once the Window is showing.


Right, what you actually want to do is create an outlet in 
MainDocument.h along the lines of:

IBOutlet NSProgressIndicator *progressIndicator;

Then if your -windowControllerDidLoadNib: method, you can do something 
like:

[progressIndicator setUsesThreadedAnimation:YES];
[progressIndicator startAnimation:self];

>
>
> But, *somewhere?,* I read that in the process of getting that Window 
> to
> show, the - (void) awakeFromNib method of each and every NSView 
> contained
> within the Window
> is called.  Therefore, I called *[self spin:itsWindow on:TRUE];* 
> within the
> CIC's *awakeFromNib*.
>
> I expected to see a rotating INSPI, or "lock washer" ... but not 
> this trip.
>
> Let me finish by asking one question: "Just where did I park my 
> brain?"


Trying to manage the animation entirely from within your progress 
indicator subclass (the view layer) is poor design as the progress 
indicator itself is ill-equipped to know whether it should be 
animating. Instead, the whole point of the MVC paradigm (which Cocoa 
relies heavily upon) is to have a controller object (in this case 
MainDocument) tell it to start animating.

I also came originally from AppleScript studio and I have to admit it 
actually makes life harder as the two approaches are very different. 
Good luck!

Mike.