I am developing an app which uses a sqlite database..
So I wrote this Singleton class as a model manager :
class ModelManager {
static let sharedInstance = ModelManager()
var database = FMDatabase(path: Utility.getPath("myDB.sqlite"))
class func getInstance() -> ModelManager {
if(sharedInstance.database == nil) {
sharedInstance.database = FMDatabase(path: Utility.getPath("myDB.sqlite"))
}
return sharedInstance
}
}
The problem is that I get compiler error when I use the sharedInstance that says use of unresolved identifier sharedInstance
For example in this class where I add data to the database
func addSData(favBuddy: favorites) -> Bool {
sharedInstance.database!.open()
let isInserted = sharedInstance.database!.executeUpdate("INSERT INTO favorties (eName, eEmail) VALUES (test, test)", withArgumentsInArray: [favorties.eName, favorties.eMail])
sharedInstance.database!.close()
return isInserted
}
Any idea how to solve this?
I'm inferring from your question that you are trying to access your shared database instance from a separate class. In that case, you need to do: ModelManager.sharedInstance
Related
I'm working on UI testing code for iOS app recently,
my UI testing code is using swift, but the project itself has some objective-c code, and I create a singleton object for launch arguments settings, which also written by swift, so I adding the #objcMembers tag to the class.
but while running the UI testing code, it seems not capable to reach the variables and functions, the singleton itself also not exists?
something I missed?
import UIKit
#if DEBUG
#objcMembers
class EALaunchArugments: NSObject {
static let sharedInstance = EALaunchArugments()
// key for property
static private let UITestingKey = "-UITesting"
var isUITesting: Bool {
let value = self.getLaunchArgumentValue(key: EALaunchArugments.UITestingKey)
return Bool(value ?? "") ?? false
}
private func getLaunchArgumentValue(key: String) -> String? {
let arguments = ProcessInfo.processInfo.arguments
let indexOfKey = arguments.firstIndex(of: key)
guard let index = indexOfKey, index != NSNotFound else {
return nil
}
guard index + 1 >= arguments.count else {
return nil
}
return arguments[index + 1]
}
func setAllLaunchArgumentsSettingsForUITesting() {
// some work
}
}
#endif
I have a simple Swift extension on NSManagedObject, in which I have a parametrized method for finding a single object - the signature looks like:
public class func findFirst<T:NSManagedObject>(inContext context : NSManagedObjectContext? = .None) -> T?
I'm trying to call this from Objective-C, but it seems like it cannot be seen. If I create a non-parameterized version I can see and call it just fine from Objective-C:
public class func findFirstUntypedWithPredicate(predicate:NSPredicate?, inContext context : NSManagedObjectContext? = .None) -> NSManagedObject?
Is there any way for ObjectiveC to be able to reach the parameterized version of the call?
I would use Self like so:
public class func findFirst(inContext context : NSManagedObjectContext? = .None) -> Self?
using the technique found here:
How can I create instances of managed object subclasses in a NSManagedObject Swift extension?
However, that causes the Swift compiler to segfault when compiling the code (Xcode 6.3.1, or Xcode 6.4 beta 2).
Edit: Here's a link with the full source of the framework I'm trying to build, including bonus Swift compiler crashes caused by templated methods:
https://www.dropbox.com/s/fixaj9ygdoi4arp/KiGiCoreData.zip?dl=0
Generic methods are not visible from Objective-C. However you can use
the ideas from How to use generic types to get object with same type to define a findFirst() class method
which returns Self? (the Swift equivalent of instancetype) without
being generic:
// Used to cast `AnyObject?` to `Self?`, `T` is inferred from the context.
func objcast<T>(obj: AnyObject?) -> T? {
return obj as! T?
}
extension NSManagedObject
{
class func entityName() -> String {
let classString = NSStringFromClass(self)
// The entity is the last component of dot-separated class name:
let components = split(classString) { $0 == "." }
return components.last ?? classString
}
// Return any matching object, or `nil` if none exists or an error occurred
class func findFirst(context : NSManagedObjectContext, withPredicate pred : NSPredicate?) -> Self? {
let name = entityName()
let request = NSFetchRequest(entityName: name)
request.predicate = pred
var error : NSError?
let result = context.executeFetchRequest(request, error: &error)
if let objects = result {
return objcast(objects.first)
} else {
println("Fetch failed: \(error?.localizedDescription)")
return nil
}
}
}
This can be used from Swift
if let obj = YourEntity.findFirst(context, withPredicate: nil) {
// found
} else {
// not found
}
and from Objective-C:
YourEntity *obj = [YourEntity findFirst:context withPredicate:nil];
I am working on developing an application in Swift. I wanted to design a system for the application that allowed for loose coupling between objects, and one strategy (which I have used successfully in other languages) was to create something I call an instance factory. It is pretty simple and here is the basic implementation I came up with in Swift:
import Foundation
private var typeGenerators = Dictionary<String, InstanceFactory.GeneratorCallback>()
public class InstanceFactory: NSObject {
public typealias GeneratorCallback = () -> AnyObject!
public class func registerGeneratorFor(typeName: String, callback: GeneratorCallback) {
typeGenerators[typeName] = callback
}
public class func instanceOf(typeName: String) -> AnyObject! {
return typeGenerators[typeName]?()
}
}
The idea is that when an object instance needs access to another object instance, rather than creating that instance outright which would more tightly couple the two objects, the first object would defer to the factory to provide the needed instance by calling the instanceOf method. The factory would know how to provide various instance types because those types would register with the factory and provide a closure that could generate the instance.
The trick is how to get the classes to register with the factory. I had previously made a similar factory in Objective-C and the way I got registration to work was to override the +load method for each class that needed to register with the factory. This worked great for Objective-C, and I figured it could work for Swift as well since I would be restricting the factory to only provide objects that are derived from NSObject. It appeared I got this to work and I spent a significant about of effort designing classes to make use of the factory.
However, after upgrading to Xcode 6.3, I discovered Apple has disallowed the usage of the load class method in Swift. Without this, I am unaware of a mechanism to allow classes to automatically register themselves with the factory.
I am wondering if there some other way to get the registration to work.
What alternatives are available that could allow classes to register with the factory, or what other techniques could be use to accomplish the same kind of loose coupling the factory provides?
I've found a possible solution to your problem after I wanted to register all ViewControllers that would be implementing a certain Protocol in my application and I ran into both this question and a possible answer.
The original was posted here: How to list all classes conforming to protocol in Swift?
I adapted it to Swift 3 and made it a bit more Swift-y and generic:
import UIKit
class ContextRoute: NSObject {
}
#objc protocol ContextRoutable {
static var route: ContextRoute { get }
}
class ContextRouter: NSObject {
private static var storedRoutes: [ContextRoute]?
static var routes: [ContextRoute] {
get {
if let storedRoutes = storedRoutes {
return storedRoutes
}
let routables: [ContextRoutable.Type] = classes(implementing: ContextRoutable.self)
let newRoutes = routables.map { routable in routable.route }
storedRoutes = newRoutes
return newRoutes
}
}
private class func classes<T>(implementing objcProtocol: Protocol) -> [T] {
let classes = classList().flatMap { objcClass in objcClass as? T }
return classes
}
private class func classList() -> [AnyObject] {
let expectedClassCount = objc_getClassList(nil, 0)
let allClasses = UnsafeMutablePointer<AnyClass?>.allocate(capacity: Int(expectedClassCount))
let autoreleasingAllClasses = AutoreleasingUnsafeMutablePointer<AnyClass?>(allClasses)
let actualClassCount:Int32 = objc_getClassList(autoreleasingAllClasses, expectedClassCount)
var classes = [AnyObject]()
for i in 0 ..< actualClassCount {
if let currentClass: AnyClass = allClasses[Int(i)],
class_conformsToProtocol(currentClass, ContextRoutable.self) {
classes.append(currentClass)
}
}
allClasses.deallocate(capacity: Int(expectedClassCount))
return classes
}
}
I tried it in my application and it works. I clocked it in the simulator and it takes 0.05s for an application that has about 12000 classes.
Consider taking the Swift approach using a protocol instead. I think the solution is actually simpler than the Objective-C approach. There are variations of this with Self constraints which are even better if you have more control over the classes.
// define a protocol to create an instance of a class
protocol FactoryInstantiable {
static func makeFactoryInstance() -> AnyObject
}
// Factory for generating new instances
public class InstanceFactory: NSObject {
public class func instanceOf(typeName: String) -> AnyObject! {
if let ProductType = NSClassFromString(typeName) as? FactoryInstantiable.Type {
return ProductType.makeFactoryInstance()
} else {
return nil
}
}
}
// your class which generally could be defined somewhere else
class MyClass {
var counter : Int
init(counter: Int) {
self.counter = 0
}
}
// extension of your class to conform to the FactoryInstantiable protocol
extension MyClass : FactoryInstantiable {
static func makeFactoryInstance() -> AnyObject {
return MyClass(counter: 0)
}
}
I'm trying to extend an Objective-C class in Swift and make it conform to the Equatable protocol. This requires to access some private members of the extended class, which the compiler doesn't let me do. What is the correct way to do it without making the private members public?
My Swift code:
import Foundation
extension ShortDate : Equatable { }
public func == (lhs: ShortDate, rhs: ShortDate) -> Bool {
if (lhs.components.year == rhs.components.year)
&& (lhs.components.month == rhs.components.month)
&& (lhs.components.day == rhs.components.day) {
return true;
}
return false;
}
Objective-C:
#interface ShortDate : NSObject<NSCopying, NSCoding> {
NSDate *inner;
NSDateComponents *components; // The date split into components.
}
...
#end
The error I'm getting:
ShortDate.swift:26:9: 'ShortDate' does not have a member named 'components'
I came across this question while trying to find a way to access a private variable of a class from one of the SDKs we use. Since we don't have or control the source code we can't change the variables to properties. I did find that the following solution works for this case:
extension ObjcClass {
func getPrivateVariable() -> String? {
return value(forKey: "privateVariable") as? String
}
open override func value(forUndefinedKey key: String) -> Any? {
if key == "privateVariable" {
return nil
}
return super.value(forUndefinedKey: key)
}
}
Overriding value(forUndefinedKey:) is optional. value(forKey:) will crash if the private variable doesn't exist on the class unless you override value(forUndefinedKey:) and provide a default value.
I believe that there is no way to access Objective-C instance variables from Swift. Only Objective-C properties get mapped to Swift properties.
I can´t get the object properties when retrieving an object from Parse Data Browser. This happened after I changed from "#NSManaged var friends" to "dynamic var friends". Even "name" show nil in User.logInWithUsernameInBackground block which is crazy because the login succeeds. The ACL for User is set to "public read".
User object:
class User : PFUser, PFSubclassing {
dynamic var friends:[User]!
dynamic var name:String!
override class func load() {
self.registerSubclass()
}
}
Retrieving the User along with the friends. println showing nil
var query = User.query()
query.includeKey("friends")
query.getObjectInBackgroundWithId(currentUser.objectId) {
(pfObject: PFObject!, error: NSError!) -> Void in
if pfObject != nil {
var user = pfObject as User
var friends = user.friends as [User]
println("friends: \(friends)") //nil
} else {
println(error)
}
}
Login. println showing nil
User.logInWithUsernameInBackground(USERNAME, password:PASSWORD) {
(user: PFUser!, error: NSError!) -> Void in
if user != nil {
println("Logged in with user: \(user.name)") //nil
} else {
println(error)
}
}
Looking a little deeper for you, it seems the hurdle is a misunderstanding of what the dynamic modifier in Swift does. Apparently, dynamic in Swift is used for Key-Value observing, not declaring a variable's accessors to be defined at runtime (what #dynamic does in Objective-C)
See this for a description of dynamic in Swift https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/AdoptingCocoaDesignPatterns.html#//apple_ref/doc/uid/TP40014216-CH7-XID_8
and this for the description of why #NSManaged works the way #dynamic does in Objective-C
https://developer.apple.com/library/prerelease/mac/documentation/Swift/Conceptual/BuildingCocoaApps/WritingSwiftClassesWithObjective-CBehavior.html#//apple_ref/doc/uid/TP40014216-CH5-XID_66
With xCode 6.1.1 I was able to get this working without the bridging header but I did need to use #NSManaged. Here's how... Just:
import Parse
at the top of the calling module. For the class declaration .swift file dynamic didn't work so I needed to use #NSManaged for the variable types to get them to link to the Parse class variables successfully. Like this:
class PSCategory : PFObject, PFSubclassing {
override class func load() {
self.registerSubclass()
}
class func parseClassName() -> String! {
return "Category"
}
#NSManaged var Name: String
}
Then in my query all the names are dynamically linked:
var query = PSCategory.query() // PFQuery(className: "Category")
query.cachePolicy = kPFCachePolicyCacheElseNetwork // kPFCachePolicyNetworkElseCache
query.maxCacheAge = 60 * 60 * 24 // One day, in seconds.
query.findObjectsInBackgroundWithBlock {
(categories: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
for abstractCategory in categories {
let category = abstractCategory as PSCategory
NSLog("Category Name: %#", category.Name)
}
} else {
NSLog("Unable to retrieve categories from local cache or network")
}
}