why is my code producing the error 'use of undeclared identifier '_predictions' when I have done exactly as instructed?

syntax:

@implementation

• (NSArray *) predictions { if (_predictions == nil) { _predictions = [[NSArray alloc] initWithObjects: @"It is certain", @"It is decidedly so", @"ALL signs say YES", @"The stars are not aligned", @"My reply is no", @"It is doubtful", @"Better not tell you now", @"Concentrate and ask again", @"Unable to answer now", nil]; } return _predictions; }

why is my code producing the error 'use of undeclared identifier '_predictions' ?

the video said that the instance variable of 'predictions' is denoted by '_predictions' but then it doesn't seem to recognise it in the implementation.

as instructed, I also declared my property variable for predictions, and the video says this automatically results in the activation of '_predictions'.