问题
I know I asked a similar question to this not long ago, but I'm still a little unsure about it. The same sort of thing happens in several places.
Instance variable used while 'self' is not set to the result of '[(super or self) init...]'
A
- (id)initWithCoder:(NSCoder *)decoder {
if (![super init]) return nil;
red = [decoder decodeFloatForKey:kRedKey]; //occurs here
green = [decoder decodeFloatForKey:kGreenKey];
blue = [decoder decodeFloatForKey:kBlueKey];
return self;
}
B
- (id)initWithFrame:(CGRect)frame title:(NSString*)str sideUp:(BOOL)up{
if(![super initWithFrame:frame]) return nil;
int y;
UIImage *img;
if(up){
img = [UIImage imageNamedTK:@"TapkuLibrary.bundle/Images/graph/popup"];
y = 5;
}else{
img = [UIImage imageNamedTK:@"TapkuLibrary.bundle/Images/graph/popdown"];
y = 14;
}
background = [[UIImageView alloc] initWithImage:img]; // occurs here
C
- (id) initWithFrame:(CGRect)frame {
if(![super initWithFrame:frame]) return nil;
UILabel *titleBackground = [[[UILabel alloc] initWithFrame:
CGRectMake(0, 0, 480, 40)] autorelease];
titleBackground.backgroundColor = [UIColor whiteColor];
[self addSubview:titleBackground];
titleLabel = [[UILabel alloc] initWithFrame:CGRectZero]; // occurs here
For block A, is this correct
self = [self init];
if( self != nil )
{
And B & C
- (id) initWithFrame:(CGRect)frame {
super = [super initWithFrame:frame]
if(super != nil)
{
回答1:
Generally, you're supposed to write:
self = [super init...]; // Potentially change "self"
if (self) {
something = x;
another = y;
}
return self;
This is because init may not return the original self value in some cases.
来源：https://stackoverflow.com/questions/8111549/obj-c-instance-variable-used-while-self-is-not-set-to-the-result-of-super