On Jul 29, 2009, at 8:35 AM, Dragos Ionel wrote:
On Wed, Jul 29, 2009 at 3:24 AM, Agha Khan <agha.k...@me.com> wrote:
On Jul 28, 2009, at 7:59 PM, Kiel Gillard wrote:
On 29/07/2009, at 12:52 PM, Agha Khan wrote:
Hi:
I have a struct
@interface PngButton : UIButton
{
@public
bool OffPos;
CGPoint horizontalLoc;
CGPoint verticalLoc;
}
@property (assign) bool OffPos;
@property (assign) CGPoint horizontalLoc;
@property (assign) CGPoint verticalLoc;
@end
No, you have an Objective-C class.
PngButton* pPngButton = [PngButton
buttonWithType:UIButtonTypeInfoDark];
[pPngButton setFrame:CGRectMake(screenRect.size.width - 70.0,
50.0, 36,
36)]; // No problem
pPngButton.verticalLoc = CGPointMake((bVerticalDisplay ==
YES) ? 250 :
410, 50.0);
I get an error
error: lvalue required as left operand of assignment
Why it is not working? I shouldn't get this error.
Any help will be very much appreciated.
Do you get any warnings?
Try this and see what happens:
pPngButton.verticalLoc = CGPointMake((bVerticalDisplay == YES ?
250.0 :
410.0), 50.0);
Kiel
Hi:
Thank you for your reply.
Oh yes. It an Objective-C class.
regardless I place (bVerticalDisplay == YES) or not. The function
silently
fails, with no warnings.
The I decided to
pPngButton.verticalLoc.x = (bVerticalDisplay == YES) ? 250 : 410;
This time I got warning.
error: lvalue required as left operand of assignment
Many thanks
-Agha
verticalLoc and x are readonly values, you cannot assign them.
use the frame property, first to retrieve it, change the x value and
then to
reassign to the button.
something like
CGFrame frame = pPngButton.frame;
frame.x = ...;
pPngButton.frame = frame;
Dragos
No, that isn't correct at all - he's declared verticalLoc as a
property that is perfectly valid to set (though, since this is the
iPhone, should be declared as nonatomic as well)
The problem is that the (simplified) code:
pPngButton.verticalLoc.x = 410;
is equivalent to writing:
[pPngButton verticalLoc].x = 410;
since pPngButton.verticalLoc is used as a getter in this case (since
your code then accesses the "x" field of the result).
This would be similar to:
CGPointMake(100,200).x = 410;
i.e., you call a function (which returns a CGPoint value) and then
you try to set one of the fields of the CGPoint value (which is then
thrown away).
Things like structures returned from a function, or scalar values,
pointers, etc... are referred to as "r-values", meaning they are
values that appear on the right hand side of an assignment - they
aren't stored in meaningful locations in memory, they just have a
"value" but not "storage". Variables (or memory locations) that can
appear on the left hand side of an assignment are called "l-values" -
they are values, but they also are stored somewhere and can have their
values changed.
So what you'd need to do is:
CGPoint pt = pPngButton.verticalLoc;
pt.x = (bVerticalDisplay == YES) ? 250 : 410;
pPngButton.verticalLoc = pt.x;
Glenn Andreas gandr...@gandreas.com
<http://www.gandreas.com/> wicked fun!
Mad, Bad, and Dangerous to Know
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