This is how i did and worked well.
1.sending single child object to Quickblox API
let qbCustomObject = QBCOCustomObject()
qbCustomObject.className = "YOUR CLASS NAME"// as given in Quickblox Custom Object
qbCustomObject.fields?.setObject(each.fullName, forKey:"name")
qbCustomObject.fields?.setObject("YOUR PARENT ID", forKey:"_parent_id")
QBRequest.createObject(qbCustomObject,className:"PLProjectMember", successBlock: { (response, contributors) in
//Handle Success
}) { (response) in
//Handle Error
}
2.Sending multiple child objects in single request to Quickblox API
var qbObjects:[QBCOCustomObject] = [QBCOCustomObject]()
for each in self!.selectedContributors{
let qbCustomObject = QBCOCustomObject()
qbCustomObject.className = "PLProjectMember"
qbCustomObject.fields?.setObject(each.fullName, forKey:"name")
qbCustomObject.fields?.setObject("YOUR PARENT ID",forKey:"_parent_id")
qbObjects.append(qbCustomObject)
}
QBRequest.createObjects(qbObjects, className:"YOUR CLASS NAME", successBlock: { (response, contributors) in
completion(true)
}) { (response) in
completion(false)
}