Passing the results from findObjectsInBackgroundWithBlock into a variable - ios

Question

I'm trying to pass the result from the query into the variable array
var petitions = [PFObject] = []
Then return that result. How I can do that in Swift?
func getPetitions(employeeId: String, employeeBusiness: String) -> [PFObject] {
var petitions: [PFObject] = []
var query = PFQuery(className:"Petitions")
query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
query.whereKey("employeeId", equalTo:employeeId)
query.whereKey("employeeBusiness", equalTo:employeeBusiness)
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]?, error: NSError?) -> Void in
if error == nil {
if let objects = objects as? [PFObject] {
NSLog("Successfully retrieved \(objects.count) petitions.")
for object in objects {
petitions.append(object)
}
}
}
}
return petitions
}

Answer 1

The query is ansynchronusly passed which means query.findObjectsInBackgroundWithBlock might not (99% won't) be finished when you return your petitions.
You can do your stuff which you want to do directly in the function:
var petitions: [PFObject] = [] //class variable
func getPetitions(employeeId: String, employeeBusiness: String) {
var query = PFQuery(className:"Petitions")
query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
query.whereKey("employeeId", equalTo:employeeId)
query.whereKey("employeeBusiness", equalTo:employeeBusiness)
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]?, error: NSError?) -> Void in
if error == nil {
if let objects = objects as? [PFObject] {
NSLog("Successfully retrieved \(objects.count) petitions.")
for object in objects {
self.petitions.append(object)
}
// update UI
// or just do whatever you want with the petitions.
}
}
}
}
Or you can write a block function:
func getPetitions(employeeId: String, employeeBusiness: String, block:PFArrayResultBlock) {
var query = PFQuery(className:"Petitions")
query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
query.whereKey("employeeId", equalTo:employeeId)
query.whereKey("employeeBusiness", equalTo:employeeBusiness)
query.findObjectsInBackgroundWithBlock(block)
}
}
To call it:
getPetitions("employeeId", "employeeBusiness", block: {
(objects: [AnyObject]?, error: NSError?) -> Void in
// do whatever you want with your objects..
// update UI
// or just do whatever you want with the petitions.
})
Another way to solve this, is to make the query synchronusly:
func getPetitions(employeeId: String, employeeBusiness: String) -> [PFObject] {
var query = PFQuery(className:"Petitions")
query.selectKeys(["petitionDate", "availableFrom", "availableTo"])
query.whereKey("employeeId", equalTo:employeeId)
query.whereKey("employeeBusiness", equalTo:employeeBusiness)
var objects = query.findObjects()
if let petititons = objects as? [PFObject] {
return petititons
} else {
return [PFObject]() // return an empty pf object array. If you want, return nil.. but the return value must be [PFObject]? if you do this.
}
}

Answer 2

You misunderstand completion blocks. You can't return a result from an async call like this. Instead you need to make the function a void (no result) and then put the code that deals with the result in your completion block.
You should refactor your getPetitions method to take it's own completion block as a parameter. Once the async Parse call is done and you're code to append the items is done, you'd then invoke the provided block.