Question

I am trying to synthesize variables in my iPhone app with

@synthesize samples=_samples;

with samples declared as

@property (strong, nonatomic) NSMutableArray *samples;

However, I get a build error claiming that _samples does not exist. Why?

Answer 1

Are you trying to access the _samples from outside the implementation file? ivars generated through @synthesize are not viewable by anything outside of the implementation where the @synthesize was called. So if you do something like this…

MyView *myView = [[MyView alloc] init];
myView._sample;

…you will see an error. See here for more details: https://stackoverflow.com/a/8511046/251012
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EDIT: All of the below is wrong. Left, so that the comments make sense

Are you declaring your ivar’s and are the names spelled correctly?

When you say something like…

@synthesize foo = _foobar;

…you need to make sure that you set the instance variable in your interface like so…

@interface MyObject : NSObject
{
    NSString *_foobar;
}
@property(nonatomic,strong) NSString *foo;
@end

To be clear, when you say foo=_foobar, foo is the base name to auto-generate the getter/setter’s, and _foobar is the name of the ivar. If no ivar is declared, @property will auto-generate one of the same name.