Sometimes I wan't to implement things like I would do it in Objective-C when working in C++. But in C++ there is no such a thing like delegation. (At least not with that name)
These are just a few notes on how to implement a delegate or delegation in C++. Is not complicated at all the only thing you need is to find the equivalents for Protocols, Delegates, in C++.
Note1: There are no protocols in C++ but you can use interfaces and multi-inheritance to accomplish this.
For example in Objective-C, let's suppose you write something like this:
@protocol UITableViewDataSource;
@interface UITableView : UIScrollView{
@private
id<UITableViewDataSource> _dataSource;
}
@end
@protocol UITableViewDataSource;
@required
- (NSInteger)tableView:(UITableView *)table numberOfRowsInSection:(NSInteger)section;
@end
Then (assuming you have the same class names) in C++ you will write something like this:
class UITableViewDataSource;
class UITableView : public UIScrollView {
UITableViewDataSource *_dataSource;
};
class UITableViewDataSource{
virtual NSInteger tableViewNumberOfRowsInSection(UITableView* tableView, NSInteger section);
}
So, how you implement your protocol?
In Objective-C:
@class MyDataSource <UITableViewDataSource> {
NSArray *array;
}
- (NSInteger)tableView:(UITableView *)table numberOfRowsInSection:(NSInteger)section;
@end
@implementation MyDataSource
- (NSInteger)tableView:(UITableView *)table numberOfRowsInSection:(NSInteger)section{
return [array count];
}
@end
In C++ (Assuming there is a NSArray class in c++)
class MyDataSource : public UITableViewDataSource {
NSArray *array;
virtual NSInteger tableViewNumberOfRowsInSection(UITableView* tableView, NSInteger section);
};
NSInteger MyDataSource::tableViewNumberOfRowsInSection(UITableView* tableView, NSInteger section){
return array->count();
}
In C++ multi-inheritance is allowed so could have a controller class that is a controller and also implements UITableViewDataSource interface. (Or in Objective-C words: conforms to UITableViewDataSource protocol)
If in Objective-C you have:
@class TableViewController : UIViewController < UITableViewDataSource > { ...
in C++ you will have:
class TableViewController : public UIViewController, public UITableViewDataSource { ...
Multi-inheritance + interfaces plays quite the same role as protocols.
Note2: There are no selectors in C++ but you can pass a method as a pointer. This is useful when you want to set a method to be called by other object.
TODO: add samples: for [object performSelector:@selector(aMethod:) withObject:argument afterDelay:0.0];
TODO: add samples for method pointers in C++
Note3: C++ does not bring any kind of concurrency APIs so you will have get your own. Boost thread, OpenCL, CUDA, OpenMP. I think OpenMP is the simplest option here. Most compilers implement it and just with a few lines of #pragma you are done. But if you get really serious and need not only multithreading but also GPU/CPU power then OpenCL is the best option, OpenCL is a young but powerful bunch of APIs for multi GPU/CPU programming, version 1.1 was just approved by Khronos group last month and with this new update we are able to run c++ code in it. The bad thing is we have to wait until Apple or your hardware vendor implements since OpenCL is just a specification.
TODO:add some links to OpenMP and Boost examples
TODO: add some links to OpenCL
