Question

I have a class for a shadowed table view that I am using in my app.

When doing the conversion to ARC, I had to change some things. With the new class, it is crashing at the following lines: (id)(inverse ? darkColor : lightColor) to (__bridge id)(inverse ? lightColor : darkColor). The console says *** -[Not A Type retain]: message sent to deallocated instance 0x4cee70

Before:

- (CAGradientLayer *)shadowAsInverse:(BOOL)inverse
{
    CAGradientLayer *newShadow = [[[CAGradientLayer alloc] init] autorelease];
    CGRect newShadowFrame =
        CGRectMake(0, 0, self.frame.size.width,
            inverse ? SHADOW_INVERSE_HEIGHT : SHADOW_HEIGHT);
    newShadow.frame = newShadowFrame;
    CGColorRef darkColor =
        [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:
            inverse ? (SHADOW_INVERSE_HEIGHT / SHADOW_HEIGHT) * 0.25 : 0.25].CGColor;
    CGColorRef lightColor =
        [self.backgroundColor colorWithAlphaComponent:0.0].CGColor;
    newShadow.colors =
        [NSArray arrayWithObjects:
            (id)(inverse ? lightColor : darkColor),
            (id)(inverse ? darkColor : lightColor),
        nil];
    return newShadow;
}

After:

- (CAGradientLayer *)shadowAsInverse:(BOOL)inverse
{
    CAGradientLayer *newShadow = [[CAGradientLayer alloc] init];
    CGRect newShadowFrame =
        CGRectMake(0, 0, self.frame.size.width,
            inverse ? SHADOW_INVERSE_HEIGHT : SHADOW_HEIGHT);
    newShadow.frame = newShadowFrame;
    CGColorRef darkColor =
        [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:
            inverse ? (SHADOW_INVERSE_HEIGHT / SHADOW_HEIGHT) * 0.25 : 0.25].CGColor;
    CGColorRef lightColor =
        [self.backgroundColor colorWithAlphaComponent:0.0].CGColor;
    newShadow.colors =
        [NSArray arrayWithObjects:
            (__bridge id)(inverse ? lightColor : darkColor),
            (__bridge id)(inverse ? darkColor : lightColor),
        nil];
    return newShadow;
}

Answer 1

Apple’s Transitioning to ARC Release Notes has a subsection titled “The Compiler Handles CF Objects Returned From Cocoa Methods”, which uses CAGradientLayer.colors as an example. It says this code will work as-is:

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        CAGradientLayer *gradientLayer = (CAGradientLayer *)[self layer];
        gradientLayer.colors = [NSArray arrayWithObjects:(id)[[UIColor darkGrayColor] CGColor],
                                                         (id)[[UIColor lightGrayColor] CGColor], nil];
        gradientLayer.startPoint = CGPointMake(0.0, 0.0);
        gradientLayer.endPoint = CGPointMake(1.0, 1.0);
    }
    return self;
}

So maybe you should try rewriting your code like this:

- (CAGradientLayer *)shadowAsInverse:(BOOL)inverse
{
    CAGradientLayer *newShadow = [[CAGradientLayer alloc] init];
    CGRect newShadowFrame =
        CGRectMake(0, 0, self.frame.size.width,
            inverse ? SHADOW_INVERSE_HEIGHT : SHADOW_HEIGHT);
    newShadow.frame = newShadowFrame;
    UIColor darkColor =
        [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:
            inverse ? (SHADOW_INVERSE_HEIGHT / SHADOW_HEIGHT) * 0.25 : 0.25];
    UIColor lightColor =
        [self.backgroundColor colorWithAlphaComponent:0.0];
    newShadow.colors = inverse
        ? [NSArray arrayWithObjects:[lightColor CGColor], [darkColor CGColor], nil]
        : [NSArray arrayWithObjects:[darkColor CGColor], [lightColor CGColor], nil];
    return newShadow;
}