Question

I have a core data entity and I ve created a NSManagedObject subclass. Say it has a attribute, "attrib1" within entity "List". In my subclass, in some cases I d like to calculate the value of attrib1, in other cases I d like to return the value from the database. I m trying to figure out how to return the database value from within my method. Example:

- (NSString *)attrib1 {
   if (flag) {
       return [self calculateValue];
   } else {
       // return value from core data, ie pass thru, but how?
       // Attempt1:
       return [super attrib1]; // Fails with  unrecognized selector 
       // Attempt2. Ends up calling this method again, recursion loop
       return [super performSelector:@selector(attrib1)];
   }
}

我应如何从作为切除1的跳板的NSManagedObject子级方法中收回“attrib1”这一特性的价值。

成就

Answer 1

首先,最好使其他财产能够从数据库中收回计算价值或取回,在这种情况下,应当留下来。你们还缺少一些接线器。因此,举例来说,法典应当照此办理:

-(NSString *)attrib1 {
    NSString *v;
    [self willAccessValueForKey:@"attrib1"];
    if(flag)
        v=[self calculateValue];
    else
        v=[self primitiveAttrib1];
    [self didAccessValueForKey:@"attrib1"];
    return v;
}

另见Ampado doc:

友情链接