KVC（Key-Value Coding）

Key-value codingis a mechanism for accessing an object’s properties indirectly, using strings to identify properties, rather than through invocation of an accessor method or accessing them directly through instance variables. In essence, key-value coding defines the patterns and method signatures that your application’s accessor methods implement.

Listing 1  Implementation of data-source method without key-value coding

- (id)tableView:(NSTableView *)tableview

objectValueForTableColumn:(id)column row:(NSInteger)row {

ChildObject *child = [childrenArray objectAtIndex:row];

if ([[column identifier] isEqualToString:@"name"]) {

return [child name];

}

if ([[column identifier] isEqualToString:@"age"]) {

return [child age];

}

if ([[column identifier] isEqualToString:@"favoriteColor"]) {

return [child favoriteColor];

}

// And so on.

}

Listing 2  Implementation of data-source method with key-value coding

- (id)tableView:(NSTableView *)tableview

objectValueForTableColumn:(id)column row:(NSInteger)row {

ChildObject *child = [childrenArray objectAtIndex:row];

return [child valueForKey:[column identifier]];

}