Perform action when all responses are retrieved from Parse

Question

I have two models, subclassing from PFObject:

** a Recipe model

class Recipe: PFObject, PFSubclassing{
  class func parseClassName() -> String {
    return "Recipe"
  }

 @NSManaged var name: String?
 var toIngredients: PFRelation! {
   return relationForKey("ingredients")
 }
}

** an Ingredient model:

class Ingredient: PFObject, PFSubclassing{
  class func parseClassName() -> String {
      return "Ingredient"
  }
  @NSManaged var category: String?
  @NSManaged var ingredient: String?
  @NSManaged var amount: NSNumber?
  @NSManaged var unit: String?
}

I found out that getting the ingredients for a single recipe, would work like this:

 let query = recipe.toIngredients.query()
 query.findObjectsInBackgroundWithBlock{....

My problem is that I have an array of recipes, that I need to get ingredients from. I need to combine the multiple asynchronous responses to use in another controller. I need to grab the whole list of ingredients, and then perfromSegueWithIdentifier.

I found this stackoverflow post: Checking for multiple asynchronous responses from Alamofire and Swift

Is this the right approach for using Parse and PFRelation?

You can do your next query in the block of previous one. Please check my answer for similar problem http://stackoverflow.com/a/34434276/4170419 — Meanteacher, Jan 06 '16 at 14:11

Cristik · Accepted Answer · 2016-01-06T16:09:28.093

Basically you need execution in parallel of multiple tasks, and be notified when all of them completed. You can achieve this if you use findObjectsInBackground() which returns a BFTask. Once you have the array of tasks, you can send them for execution in parallel (more details here):

let tasks = recipes.map { $0.toIngredients.query().findObjectsInBackground() }
let aggregateTask = BFTask(forCompletionOfAllTasks: tasks)
aggregateTask.continueWithBlock { task in
    if task.error() { 
        // handle the error
    } else {
       // grab the results, perform the seque
    }
}

Perform action when all responses are retrieved from Parse

1 Answers1