Using RACCommand with MVVM pattern, sending parameters to ViewModel - objective-c

Question

I'm using ReactiveCocoa framework at my app for the power using MVVM design pattern.
So for every Controller, I have a ViewModel. and the Controller is binded to his ViewModel.
UIButton binding will look like so:
#implementation HomeController
-(void) bindViewModel {
self.viewHeader.buttonSide.rac_command = self.viewModel.execiteFullPortfolio;
}
It all works well, But when i would like to pass parameters to the ViewModel, I'm not sure what is the right way to do so...
Say I have a UICollectionView of Stocks, and every click on a specific stock, I would like to navigate to thats stocks profile page.
That logic should be done at the ViewModel, But how do i get the stock passed with the RACCommand?
What I'm currently doing is :
#implementation HomeController
-(void) bindViewModel {
__unsafe_unretained HomeController *weakSelf = self;
self.viewPortfolioPusherView.scrollGainView.blockSelect = ^ (STStock *stock){
weakSelf.viewModel.selectedStock = stock;
[weakSelf.viewModel.executeGoToStock execute:[RACSignal empty]];
};
}
#implementation HomeViewModel
-(void) initialization {
self.executeGoToStock = [[RACCommand alloc] initWithSignalBlock:^RACSignal *(id input) {
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf moveToSelectedStock];
});
return [RACSignal empty];
}];
}
-(void) moveToSelectedStock {
[self stockProfileControllerLazy];
self.stockProfileController.stock = self.selectedStock;
[Navigator pushController:self.stockProfileController fromController:[self.delegate controller]];
}
I'm sure this is not best practice! So I'm asking, What is??
Thanks .

Answer 1

Why not just pass the STStock instance into the call to execute on the command, rather than an empty signal?
[weakSelf.viewModel.executeGoToStock execute:stock];
Then:
self.executeGoToStock = [[RACCommand alloc] initWithSignalBlock:^RACSignal *(STStock *stock) {
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf moveToSelectedStock:stock];
});
return [RACSignal empty];
}];
You obviously need to modify moveToSelectedStock to take a parameter as well. However, I'd go a bit further an implement an RACCommand on your Navigator that does that. Furthermore, I'd make a separate view model for an instance of STStock rather than a collection. So, when you select a stock, it might look something a little more like this:
StockViewModel *viewModel = [[StockViewModel alloc] initWithStock:stock];
[[Navigator pushViewModel] execute:viewModel];
This obviously omits a few details. For example, my navigator maps view model classes to controller classes. When a view model is pushed, it creates the corresponding controller, and binds the view model to it.