My Code
isFiltering = true
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let words = textInSearchField.components(separatedBy: " ")
for word in words{
if (word).count == 0{
continue
}
let firstNamePredicate = NSPredicate(format: "firstName contains[c] %#", word)
let lastNamePredicate = NSPredicate(format: "lastName contains[c] %#", word)
let idPredicate = NSPredicate(format: "id contains[c] %#", word)
let orPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.or, subpredicates: [firstNamePredicate, lastNamePredicate, idPredicate])
clientsEntity.predicate = orPredicate
clientResults = try! context.fetch(clientsEntity) as! [NSManagedObject]
let sort:NSSortDescriptor = NSSortDescriptor(key:"dateSorted", ascending: false)
for (index, ob) in clientResults.enumerated(){
let relationship = ob.value(forKey: "assessed_by") as! NSSet
let array = relationship.sortedArray(using: [sort]) as! [NSManagedObject]
for item in array.enumerated() {
results.append(item.element)
print(results)
}
}
My data model:
I am using a tableView to display my data which works great, now I have implemented a filter function which allows the user to search based on a Clients first name, last name, id etc using NSCompoundPredicate.
I then sort the resulting [NSManagedObject] by date using NSSortDescriptor, my aim is to set my clientResults variable to contain the SORTED contents of the NSSet. My print statement only outputs that there is one Assessment inside the results variable when in actual fact the NSSet contains two of these NSManagedObjects.
let sort:NSSortDescriptor = NSSortDescriptor(key:"dateSorted", ascending: false)
for (index, ob) in clientResults.enumerated(){
let relationship = ob.value(forKey: "assessed_by") as! NSSet
let array = relationship.sortedArray(using: [sort]) as! [NSManagedObject]
// MARK - I enumerate the contents of the sorted array.
for item in array.enumerated() {
results.append(item.element)
print(results)
}
}
What is the best practice for assigning the contents of the NSSet to a variable of type [NSManagedObject]?
Thank you.
If you know that elements in NSSet are of type NSManagedObject why not just do
let managedObjectsArray = set.allObjects
or if you want to make sure it is of correct type you can do:
if let managedObjectsArray = set.allObjects as? [NSManagedObject] {
//do what you want with [NSManagedObject] array
}
Related
hello community I am a novice and this is my first question.
how to change all the attributes of an entity and be able to change all my Core Data elements,
because I can only change the first attribute of an entity but not all my data records.
Here in this function I can only change the name
and then I get this following error has the line:
let objectUpdate = test[0] : Thread 1: Fatal error: Index out of range
func updateData() {
var newName = ""
var newPrenom = ""
newName = name.text!
newPrenom = prenom.text!
let managedContext = AppDelegate.viewContext
let fetchRequest : NSFetchRequest<NSFetchRequestResult> = NSFetchRequest.init(entityName: "Person")
fetchRequest.predicate = NSPredicate(format: "name = %#", newName)
do {
fetchRequest.predicate = NSPredicate(format: "prenom = %#", newPrenom)
let test = try! managedContext.fetch(fetchRequest) as! [NSManagedObject]
let objectUpdate = test[0]
objectUpdate.setValue(newName,forKey: "name")
objectUpdate.setValue(newPrenom, forKey: "prenom")
do {
try managedContext.save()
}
catch {
print(error)
}
} catch {
print(error)
}
}
There are a number of ways we can avoid this error.
Unwrapping optional .first value
Swift's Collection gives us safe way to get first item, simply by accessing the first property on a given collection. It will return an Optional<Element> value so we need to unwrap it first either by using if let of guard let
if let object = test.first {
// do something with object
}
or
guard let object = test.first else { return }
// do something with object
Checking if value at index exists
It's often a good idea to check for a specific index within the indices property before accessing the value behind it.
if test.indices.contains(0) {
let object = test[0]
// do something with object
}
These hints should prevent your code from crashing again.
Other Suggestions
This is not really safe or clean:
var newName = ""
var newPrenom = ""
newName = name.text!
newPrenom = prenom.text!
We can make it much cleaner and most importantly safer by using a guard statement
guard let newName = name.text, let newPrenom = prenom.text else { return }
Two important things happened here:
No more force-unwrapping the optional values of text [which could cause a crash]
The properties are now immutable, meaning we can be sure that what we are saving to the CoreDate is what was retreived at the beginning of the function
Since the line:
let test = try! managedContext.fetch(fetchRequest) as! [NSManagedObject]
is already wrapped in the do-catch clause, you can safely remove forced try! and replace it with try.
let test = try managedContext.fetch(fetchRequest) as! [NSManagedObject]
Let's use types! On this line you create a NSFetchRequest object for some entity named "Person".
let fetchRequest : NSFetchRequest<NSFetchRequestResult> = NSFetchRequest.init(entityName: "Person")
I am guessing CoreData have generated for you a NSManagedObject subclass, named Person. If this is true, you could rewrite it like this:
let fetchRequest = NSFetchRequest<Person>(entityName: "Person")
With the previous tip implemented, we can now get rid of as! [NSManagedObject] from this line:
let test = try managedContext.fetch(fetchRequest) as! [NSManagedObject]
Since the NSFetchRequest object is now nicely typed, we can take advantage of it by rewriting it like this:
let test: [Person] = try managedContext.fetch(fetchRequest)
So we are using proper types now? cool! Lets now improve this:
objectUpdate.setValue(newName,forKey: "name")
objectUpdate.setValue(newPrenom, forKey: "prenom")
by rewriting this and using properties on Person object
objectUpdate.name = newName
objectUpdate.prenom = newPrenom
No need for introducing second level of do-catch clause, since we are already in one!
do {
try managedContext.save()
}
catch {
print(error)
}
you can easily replace it with just the save() call, like this:
try managedContext.save()
Are you sure these predicates are what you want?
fetchRequest.predicate = NSPredicate(format: "name = %#", newName)
fetchRequest.predicate = NSPredicate(format: "prenom = %#", newPrenom)
What I can read from them is that you are fetching Person object where the name is newName and prenom is newPrenom and then you update it with the same exact values? Are you using some kind of identification of users? like id: Int or id: UUID? It would make much more sense to write something like this
let id: Int = // ID of the user you are currently editing
fetchRequest.predicate = NSPredicate(format: "id == \(id)")
if you are not using any id's, you could try storing the initial values of name and prenom
// in cell declaration - set when you configure your cell
var initialName: String?
var initialPrenom: String?
// then in your function:
fetchRequest.predicate = NSPredicate(format: "name = %#", initialName)
fetchRequest.predicate = NSPredicate(format: "prenom = %#", initialPrenom)
But I just noticed you also override you first predicate with the second one. You need to use NSCompoundPredicate
fetchRequest.predicate = NSCompoundPredicate(
type: .and, subpredicates: [
NSPredicate(format: "name = %#", initialName),
NSPredicate(format: "prenom = %#", initialPrenom)
]
)
Suggested version
func updateData() {
guard let newName = name.text, let newPrenom = prenom.text else { return }
let managedContext = AppDelegate.viewContext
let fetchRequest = NSFetchRequest<Person>(entityName: "Person")
fetchRequest.predicate = NSCompoundPredicate(
type: .and, subpredicates: [
NSPredicate(format: "name = %#", initialName),
NSPredicate(format: "prenom = %#", initialPrenom)
]
)
do {
let objects: [Person] = try managedContext.fetch(fetchRequest)
guard let object = objects.first else { return }
object.name = newName
object.prenom = newPrenom
try managedContext.save()
} catch {
print(error)
}
}
If the index 0 is out of range, it means that the array is empty. Before accessing it, add
if test.isEmpty{
return //the fetch request didn't return any values
}
My Data Model
A Client can have many Assessments but an Assessment can only have one Client as an inverse relationship. My aim is to fetch all the Assessments that a Client has and also filter based on the "firstName" property of the initial Client.
My Filter Function:
func filterData(){
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let words = textInSearchField.components(separatedBy: " ")
for word in words{
if (word).count == 0{
continue
}
let firstNamePredicate = NSPredicate(format: "firstName contains[c] %#", word)
let lastNamePredicate = NSPredicate(format: "lastName contains[c] %#", word)
let idPredicate = NSPredicate(format: "id contains[c] %#", word)
// I am using a Compound Predicate so that I can filter by first name, last name but also the id property.
let orPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.or, subpredicates: [firstNamePredicate, lastNamePredicate, idPredicate])
clientsEntity.predicate = orPredicate
// results is an array of type [NSManagedObject], I am using the compound predicate I created above to fetch specific clients.
results = try! context.fetch(clientsEntity) as! [NSManagedObject]
}
}
I essentially want to get all the Assessments of a Client filtering by the firstName, lastName or ID. Is NSPredicate the best approach?
Thank you.
In my code below I am using NSPredicates specifically I am using NSCompoundPredicate to check for multiple different parameters in my search function. How would I go about searching with both the First Name AND Last Name, I am currently using AND but it does not return anything in my UITableView. All my other predicates listed in the compound predicate work great.
func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
textInSearchField = searchBar.text!
if searchBar.text == ""{
print("Searching for all clients.")
retrieveClients()
view.endEditing(true)
clientTableView.reloadData()
}else{
print("Enter a client name to search.")
isFilteringSearch = true
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let firstAndLast = NSPredicate(format: "firstName = %# AND lastName = %#", textInSearchField)
let firstNamePredicate = NSPredicate(format: "firstName = %#", textInSearchField)
let lastNamePredicate = NSPredicate(format: "lastName = %#", textInSearchField)
let idPredicate = NSPredicate(format: "id = %#", textInSearchField)
let orPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.or, subpredicates: [firstAndLast,firstNamePredicate, lastNamePredicate, idPredicate])
clientsEntity.predicate = orPredicate
clients = try! context.fetch(clientsEntity) as! [NSManagedObject]
view.endEditing(true)
clientTableView.reloadData()
}
}
Something to bear in mind is that I still need to be able to use
LogicalType.or since I want to have the option for the user to search by first name, last name but also a combination of both for example Harold Finch or Finch/Harold etc.
Cheers!
let firstAndLast = NSPredicate(format: "firstName = %# AND lastName = %#", textInSearchField)
let firstNamePredicate = NSPredicate(format: "firstName = %#", textInSearchField)
let lastNamePredicate = NSPredicate(format: "lastName = %#", textInSearchField)
let idPredicate = NSPredicate(format: "id = %#", textInSearchField)
let orPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.or, subpredicates: [firstAndLast,firstNamePredicate, lastNamePredicate, idPredicate])
I hope that for orPredicate, it should be [firstAndLast, idPredicate] instead, but you didn't make it work. Else you need to rethink about it, that's your orPredicate current logic:
if ((a == x AND b == x) OR (a == x) OR (b == x) OR (c = x)) {
}
The (a == x AND b == x) is useless.
There is an issue on that line:
let firstAndLast = NSPredicate(format: "firstName = %# AND lastName = %#", textInSearchField)
You have two placeholders (%#), but only one argument (textInSearchField).
let firstAndLast = NSPredicate(format: "firstName = %# AND lastName = %#", textInSearchField, textInSearchField)
Thank for the help, I ended up using an alternative method with contains[c] my code is below for anyone who needs help with a similar function, you can use contains[c](contains character) to search via character specifically this applies to all strings i.e first name or last name and in my case also an ID which is stored as a String also.
func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
textInSearchField = searchBar.text!
if searchBar.text == ""{
retrieveClients()
view.endEditing(true)
clientTableView.reloadData()
}else{
isFilteringSearch = true
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let words = textInSearchField.components(separatedBy: " ")
for word in words{
if (word).count == 0{
continue
}
let firstNamePredicate = NSPredicate(format: "firstName contains[c] %#", word)
let lastNamePredicate = NSPredicate(format: "lastName contains[c] %#", word)
let idPredicate = NSPredicate(format: "id contains[c] %#", word)
let orPredicate = NSCompoundPredicate(type: NSCompoundPredicate.LogicalType.or, subpredicates: [firstNamePredicate, lastNamePredicate, idPredicate])
clientsEntity.predicate = orPredicate
}
clients = try! context.fetch(clientsEntity) as! [NSManagedObject]
view.endEditing(true)
clientTableView.reloadData()
}
}
I followed the second answer on this post NSPredicate: Combine CONTAINS with IN
Thank You
I implements OR filter,
if user types "NBA LA",
Any item in this array "appDel.dataFetcher?.appTitles" will be searched with OR mode.
However, I don't know how to implement AND mode.
That is any selected item must have NBA and LA in its text at the same time
OR SEARCH
let searchTerms = searchController.searchBar.text!.characters.split{$0 == " "}.map(String.init)
for term: String in searchTerms {
let searchPredicate = NSPredicate(format: "SELF CONTAINS[c] %#", term)
let array = ((appDel.dataFetcher?.appTitles)! as NSArray).filteredArrayUsingPredicate(searchPredicate)
searchResult += array as! [String]
}
let mySet = Set<String>(searchResult)
You can build up your resulting AND predicate using NSCompoundPredicate(andPredicateWithSubpredicates:) like below:
let predicates = searchTerms.map {
return NSPredicate(format: "SELF CONTAINS[c] %#", $0)
}
let searchPredicate = NSCompoundPredicate(andPredicateWithSubpredicates: predicates)
let searchResult = ((appDel.dataFetcher?.appTitles)! as NSArray).filteredArrayUsingPredicate(searchPredicate)
let mySet = Set<String>(searchResult)
FYI, you can split your text much more easier using componentsSeparatedByString:
let searchTerms = searchController.searchBar.text!.componentsSeparatedByString(" ")
I'm using the following code to fetch all the data in "category".
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
let managedContext = appDelegate.managedObjectContext!
let fetchRequest = NSFetchRequest(entityName:"category")
let fetchedResults = managedContext.executeFetchRequest(fetchRequest, error: &error) as [NSManagedObject]?
How do I only brings categories where the "type" is equal to "products"?
To "filter" results in Core Data, use NSPredicate like so:
let filter = "products"
let predicate = NSPredicate(format: "type = %#", filter)
fetchRequest.predicate = predicate
So, in the below example
In the first step, we will add give the value we want to filter.
In the second step, we will add a predicate in which we will give the DB key we want to get the value in my case is "id" and besides this a value, we want to filter.
In the Third step assign the entity name where your all data has saved in the NSFetchRequest.
After that assign the predicate.
Use context object to fetch the object.
private let context = (NSApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let filter = id
let predicate = NSPredicate(format: "id = %#", filter)
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName:"TodoListItem")
fetchRequest.predicate = predicate
do{
let fetchedResults = try context.fetch(fetchRequest) as! [NSManagedObject]
print("Fetch results")
if let task = fetchedResults.first as? TodoListItem{
print(task)
}
// try context.save()
}catch let err{
print("Error in updating",err)
}
You can use .filter on the fetchedResults.