In my Objective C code I had this:
if ([view conformsToProtocol:#protocol(UITextInputTraits)]) {
id<UITextInputTraits> field = view;
field.enablesReturnKeyAutomatically = YES;
}
Now I'm trying to convert that to swift, so I did this:
if var field = view as? UITextInputTraits {
field.enabledReturnKeyAutomatically = true
}
I'm getting a compiler error saying that 'field' is immutable. What's the right way to accomplish this?
The problem is caused by Swift's peculiar way of dealing with optional protocol requirements. Optional protocol properties have no setter. (I regard this as a bug in the language.) You'll have to work around it.
You can say (horrible):
switch view {
case let field as UITextField:
field.enablesReturnKeyAutomatically = true
case let field as UITextView:
field.enablesReturnKeyAutomatically = true
default: break
}
Another way (equally horrible):
let setter = #selector(setter:UITextInputTraits.enablesReturnKeyAutomatically)
if view.responds(to:setter) {
view.perform(setter, with: 1 as NSNumber)
}
Related
The Apple documentation shows an unsettling blank space under the 'Creating a Dictionary' section of the UIKit reference here.
Has anyone found a replacement for the NSDictionaryOfVariableBindings macro, or are we expected to just write our own?
EDIT - According to this perhaps the right approach is to write a global function to handle this? Looks like complex macros are out entirely.
According to Apple source code:
NSDictionaryOfVariableBindings(v1, v2, v3) is equivalent to [NSDictionary dictionaryWithObjectsAndKeys:v1, #"v1", v2, #"v2", v3, #"v3", nil];
So in Swift you can do the same using:
let bindings = ["v1": v1, "v2": v2, "v3": v3]
NSDictionaryOfVariableBindings is, as you say, a macro. There are no macros in Swift. So much for that.
Nonetheless, you can easily write a Swift function to assign string names to your views in a dictionary, and then pass that dictionary into constraintsWithVisualFormat. The difference is that, unlike Objective-C, Swift can't see your names for those views; you will have to let it make up some new names.
[To be clear, it isn't that your Objective-C code could see your variable names; it's that, at macro evaluation time, the preprocessor was operating on your source code as text and rewriting it — and so it could just use the text of your variable names both inside quotes (to make strings) and outside (to make values) to form a dictionary. But with Swift, there is no preprocessor.]
So, here's what I do:
func dictionaryOfNames(arr:UIView...) -> Dictionary<String,UIView> {
var d = Dictionary<String,UIView>()
for (ix,v) in arr.enumerate(){
d["v\(ix+1)"] = v
}
return d
}
And you call it and use it like this:
let d = dictionaryOfNames(myView, myOtherView, myFantasicView)
myView.addConstraints(
NSLayoutConstraint.constraintsWithVisualFormat(
"H:|[v2]|", options: nil, metrics: nil, views: d)
)
The catch is that it is up to you to realize that the name for myOtherView in your visual format string will be v2 (because it was second in the list passed in to dictionaryOfNames()). But I can live with that just to avoid the tedium of typing out the dictionary by hand every time.
Of course, you could equally have written more or less this same function in Objective-C. It's just that you didn't bother because the macro already existed!
That functionality is based on macro expansion which is currently not supported in Swift.
I do not think there is any way to do something similar in Swift at the moment. I believe you cannot write your own replacement.
I'm afraid you'll have to manually unroll the dictionary definition, even if it means repeating each name twice.
So I hacked something together which seems to work:
func dictionaryOfVariableBindings(container: Any, views:UIView...) -> Dictionary<String, UIView> {
var d = Dictionary<String, UIView>()
let mirror = Mirror(reflecting: container)
let _ = mirror.children.compactMap {
guard let name = $0.label, let view = $0.value as? UIView else { return }
guard views.contains(view) else { return }
d[name] = view
}
return d
}
Usage:
let views = dictionaryOfVariableBindings(container: self, views: imageView)
ObjC runtime to the rescue!
i created an alternate solution, but it only works if each of the views are instance variables of the same object.
func DictionaryOfInstanceVariables(container:AnyObject, objects: String ...) -> [String:AnyObject] {
var views = [String:AnyObject]()
for objectName in objects {
guard let object = object_getIvar(container, class_getInstanceVariable(container.dynamicType, objectName)) else {
assertionFailure("\(objectName) is not an ivar of: \(container)");
continue
}
views[objectName] = object
}
return views
}
can be used like this:
class ViewController: UIViewController {
var childA: UIView = {
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
view.backgroundColor = UIColor.redColor()
return view
}()
var childB: UIButton = {
let view = UIButton()
view.setTitle("asdf", forState: .Normal)
view.translatesAutoresizingMaskIntoConstraints = false
view.backgroundColor = UIColor.blueColor()
return view
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(childA)
self.view.addSubview(childB)
let views = DictionaryOfInstanceVariables(self, objects: "childA", "childB")
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[childA]|", options: [], metrics: nil, views: views))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[childB]|", options: [], metrics: nil, views: views))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[childA][childB(==childA)]|", options: [], metrics: nil, views: views))
}
}
unfortunately you still have to type the variable name in as a string, but it will at least assert if there is a typo. this definitely won't work in all situations, but helpful nonetheless
Based on https://stackoverflow.com/a/55086673/1058199 by cherpak-evgeny, this UIViewController extension assumes that the container is self, the current viewController instance.
extension UIViewController {
// Alex Zavatone 06/04/2019
// Using reflection, get the string name of the UIView properties passed in
// to create a dictionary of ["viewPropertyName": viewPropertyObject…] like
// Objective-C's NSDictionaryForVariableBindings.
func dictionaryOfBindings(_ arrayOfViews:[UIView?]) -> Dictionary<String, UIView> {
var bindings = Dictionary<String, UIView>()
let viewMirror = Mirror(reflecting: self)
let _ = viewMirror.children.compactMap {
guard let name = $0.label, let view = $0.value as? UIView else { return }
guard arrayOfViews.contains(view) else { return }
bindings[name] = view
}
return bindings
}
}
Use it like so from within your viewController:
let viewArray = [mySwitch, myField, mySpinner, aStepper, someView]
let constraintsDictionary = dictionaryOfBindings(viewArray)
Tested in Xcode 10.2.1 and Swift 4.2.
Many thanks to Cherpak Evgeny for writing it in the first place.
Once you've stored all your views as properties, you could also use reflection like so:
extension ViewController {
func views() -> Dictionary<String, AnyObject> {
var views = dictionaryOfProperties()
views.forEach {
if !($1 is UIView) {
views[$0] = nil
}
}
return views
}
}
extension NSObject {
func dictionaryOfProperties() -> Dictionary<String, AnyObject> {
var result = Dictionary<String, AnyObject>()
let mirror = Mirror(reflecting: self)
for case let(label?, value) in mirror.children {
result[label] = value as? AnyObject
}
return result
}
}
I'm trying to use a control called MZFormSheetController in swift. In the example given it provides a property as a completion handler, if I understand correctly, but I'm having difficulties translating it in Swift. Any help would be appreciated.
This is in the obj-c example.
controller.didPresentContentViewControllerHandler = ^(UIViewController *content) {
NSLog(#"DID PRESENT");
[self setNeedsStatusBarAppearanceUpdate];
};
I tried many variations and did an extensive search in the web but I could not find anything that could help me so I'm stuck here
controller.didPresentContentViewControllerHandler = (content:UIViewController() -> () {
println("did present1")
})
Here are the relevant docs: Cocoa Docs:: MZFormSheetPresentationController:: didPresentContentViewControllerHandler
If you need to access the view controller then do it like this,
controller.didPresentContentViewControllerHandler = {
controller in
println("did present1")
}
Or if you dont need the reference to the view controller, you can simply do,
let controller = Controller()
controller.didPresentContentViewControllerHandler = {
_ in
println("did present1")
}
Try add a variable after opening brace
controller.didPresentContentViewControllerHandler = {
vc in
println("did present1")
})
After experimenting with a few little Swift programs, I decided my next step was to port a single module in an Objective-C program into Swift to see what steps were required. I had a number of issues, so I thought I'd post my process and results here in case others might find it useful.
I also created a table to help me remember the different conversions. Unfortunately, StackOverflow doesn't support tables, so I posted these conversions as a Github gist here.
Although Apple will undoubtedly provide an Xcode Refactor to convert from Objective-C to Swift, converting one manually is a great way to get familiar with the differences between the two languages. There is so much 'muscle memory' involved in a language you know well, and this is a great way to get familiar with the new syntax. As promised by Apple, it turns out the languages share so many common ideas, that it's mostly a mechanical process (as opposed to porting from, say C++ or even traditional C).
Note that this process uses none of the exciting new features of Swift, it only gets the code straight across. I should mention that moving to Swift will restrict any backwards compatability to iOS 7 or OS X 10.9. I also ran into a couple of issues (with workarounds below) that I'm sure are just due to the first beta release status of the project, so may not be required in future versions.
I chose iPhoneCoreDataRecipes and picked a module that didn’t rely on a lot of others: IngredientDetailViewController. If you'd like to follow along, check out my "answer" below.
Hope this is of use.
0) Download a copy of the project here and open Recipes.xcodeproj in Xcode version 6.
1) Choose File>New File…>iOS Source>Swift File> IngredientDetailViewController (Folder: Classes, Group: Recipe View Controllers)
2) Reply Yes to “Would you like to configure an Objective-C bridging header?”
3) Copy the first three lines below from Recipes_Prefix.pch and the next three from IngredientDetailViewController.m into Recipes-Bridging-Header.h. If you do further files, obviously don't duplicate lines, and remove any files that you've converted to Swift. I haven't found any where that documents the need for the Cocoa lines, given that they're imported in the swift file, but ...
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>
#import "Recipe.h"
#import "Ingredient.h"
#import "EditingTableViewCell.h"
4) Copy/paste the text from both the IngredientDetailViewController.h file and the IngredientDetailViewController.m files into IngredientDetailViewController.swift.
5) Delete both IngredientDetailViewController.h and .m files from project.
6) Do a global Find-and-Replace from #import "IngredientDetailViewController.h" to #import "Recipes-Swift.h" (Only one conversion in this case, and again for further files, don't duplicate this line in your Objective-C modules.)
7) Check the Project>Targets>Recipes>Build Settings Runpath Search Paths. If it shows $(inherited), remove this line or you'll get an error on launch about "no image found"
8) Convert Objective-C syntax in IngredientDetailViewController.swift to Swift. See the GitHub Gist mentioned above the substitutions required, or below for my converted version.
9) You may need to update the IB links. Do a Find>Find in Files on IngredientDetailViewController and select the one in Interface Builder. Open the Identity Inspector in the right-hand column. Select IngredientDetailViewController in the Class field, type xxx or something and tab.
10) Build and Run. Note that after going into a recipe, you must tap Edit and then the info button of an ingredient to activate IngredientDetailViewController
12) Congrats on building your first mixed Swift/Objective-C program!
Here's my cut at this particular module:
``
class IngredientDetailViewController: UITableViewController {
var recipe: Recipe!
var ingredient: Ingredient! {
willSet {
if let newIngredient = newValue {
self.ingredientStr = newIngredient.name
self.amountStr = newIngredient.amount
} else {
self.ingredientStr = ""
self.amountStr = ""
}
}
}
init(nibName nibNameOrNil: String!, bundle nibBundleOrNil: NSBundle!) {
super.init(nibName:nibNameOrNil, bundle: nibBundleOrNil?)
}
init(coder aDecoder: NSCoder!) {
super.init(coder: aDecoder)
}
init(style: UITableViewStyle) {
super.init(style: style)
}
// MARK: table's data source
var ingredientStr: String?
var amountStr: String?
// view tags for each UITextField
let kIngredientFieldTag = 1
let kAmountFieldTag = 2
override func viewDidLoad () {
super.viewDidLoad()
self.title = "Ingredient"
self.tableView.allowsSelection = false
self.tableView.allowsSelectionDuringEditing = false
}
override func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int {
return 2
}
override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! {
let IngredientsCellIdentifier = "IngredientsCell"
let cell = tableView.dequeueReusableCellWithIdentifier(IngredientsCellIdentifier, forIndexPath: indexPath ) as EditingTableViewCell
if (indexPath.row == 0) {
// cell ingredient name
cell.label.text = "Ingredient"
cell.textField.text = self.ingredientStr
cell.textField.placeholder = "Name"
cell.textField.tag = kIngredientFieldTag
}
else if (indexPath.row == 1) {
// cell ingredient amount
cell.label.text = "Amount"
cell.textField.text = self.amountStr
cell.textField.placeholder = "Amount"
cell.textField.tag = kAmountFieldTag
}
return cell
}
#IBAction func save (sender: AnyObject!) {
if let context = self.recipe.managedObjectContext {
if (!self.ingredient) {
self.ingredient = NSEntityDescription.insertNewObjectForEntityForName("Ingredient",
inManagedObjectContext:context) as Ingredient
self.recipe.addIngredientsObject(self.ingredient)
self.ingredient.displayOrder = self.recipe.ingredients.count
}
// update the ingredient from the values in the text fields
let cell = self.tableView.cellForRowAtIndexPath(NSIndexPath(forRow:0, inSection:0)) as EditingTableViewCell
self.ingredient.name = cell.textField.text
// save the managed object context
var error: NSError? = nil
if !context.save( &error) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate.
You should not use this function in a shipping application, although it may be
useful during development. If it is not possible to recover from the error, display
an alert panel that instructs the user to quit the application by pressing the Home button.
*/
println("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
// if there isn't an ingredient object, create and configure one
self.parentViewController.dismissViewControllerAnimated(true, completion:nil)
}
#IBAction func cancel(sender: AnyObject!) {
self.parentViewController.dismissViewControllerAnimated(true, completion:nil)
}
func textFieldDidEndEditing(textField:UITextField) {
// editing has ended in one of our text fields, assign it's text to the right
// ivar based on the view tag
//
switch (textField.tag)
{
case kIngredientFieldTag:
self.ingredientStr = textField.text
case kAmountFieldTag:
self.amountStr = textField.text
default:
break
}
}
}
I'm subclassing NSButtonCell to customize the drawing (customizable theme). I'd like to customize the way checkboxes and radio buttons are drawn.
Does anyone know how to detect whether a button is a checkbox or radio button?
There is only -setButtonType:, no getter, and neither -showsStateBy nor -highlightsBy seem to give any unique return values for checkboxes that don't also apply to regular push buttons with images and alternate images.
So far I've found two (not very pretty) workarounds, but they're the kind of thing that'd probably get the app rejected from MAS:
Use [self valueForKey: #"buttonType"]. This works, but since the method is not in the headers, I presume this is something Apple wouldn't want me to do.
Override -setButtonType: and -initWithCoder: to keep track of the button type when it is set manually or from the XIB. Trouble here is the XIB case, because the keys used to save the button type to disk are undocumented. So again, I'd be using private API.
I'd really like this to be a straight drop-in replacement for NSButtonCell instead of forcing client code to use a separate ULIThemeSwitchButtonCell class for checkboxes and a third one for radio buttons.
A button does not know anything about its style.
From the documentation on NSButton
Note that there is no -buttonType method. The set method sets various button properties that together establish the behavior of the type. -
You could use tag: and setTag: (inherited by NSButton from NSControl) in order to mark the button either as a checkbox or a radio button. If you do that programatically then you should define the constant you use. You can also set the tag in Interface Builder, but only as an integer value (magic number).
In initWithCoder, here is my adaptation of the BGHUDButtonCell.m solution, updated for Mac OS Sierra:
-(id)initWithCoder:(NSCoder *)aDecoder {
if ( !(self = [super initWithCoder: aDecoder]) ) return nil;
NSImage *normalImage = [aDecoder decodeObjectForKey:#"NSNormalImage"];
if ( [normalImage isKindOfClass:[NSImage class]] )
{
DLog( #"buttonname %#", [normalImage name] );
if ( [[normalImage name] isEqualToString:#"NSSwitch"] )
bgButtonType = kBGButtonTypeSwitch;
else if ( [[normalImage name] isEqualToString:#"NSRadioButton"] )
bgButtonType = kBGButtonTypeRadio;
}
else
{
// Mac OS Sierra update (description has word "checkbox")
NSImage *img = [self image];
if ( img && [[img description] rangeOfString:#"checkbox"].length )
{
bgButtonType = kBGButtonTypeSwitch;
}
}
}
This is strange to me that it's missing from NSButton. I don't get it. That said, it's easy enough to extend NSButton to store the last set value:
import Cocoa
public class TypedButton: NSButton {
private var _buttonType: NSButton.ButtonType = .momentaryLight
public var buttonType: NSButton.ButtonType {
return _buttonType
}
override public func setButtonType(_ type: NSButton.ButtonType) {
super.setButtonType(type)
_buttonType = type
}
}
Swift 5.5
This is my approach. I use a standard naming convention in my app that relies on plain language identifiers. All my UI elements incorporate their respective property names and what type of UI element is associated with the property. It can make for some pretty long IBOutlet and IBAction names, but remembering tag numbers is way too complicated for me.
For example:
#IBOutlet weak var serveBeerCheckbox: NSButton!
#IBOutlet weak var headSize0RadioButton: NSButton!
#IBOutlet weak var headSize1RadioButton: NSButton!
#IBOutlet weak var headSize2RadioButton: NSButton!
\\ etc.
If there are UI properties that need to be stored, I name those without the type of UI element:
var serveBeer: Bool = true
var headSize: Int = 1
Bare bones example:
import Cocoa
class ViewController: NSViewController {
#IBOutlet weak var serveBeerCheckbox: NSButton!
#IBOutlet weak var headSize0RadioButton: NSButton!
#IBOutlet weak var headSize1RadioButton: NSButton!
#IBOutlet weak var headSize2RadioButton: NSButton!
var serveBeer: Bool = true
var headSize: Int = 1
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func buttonClicked(button: NSButton) {
guard let identifier = button.identifier else { return }
if identifier.rawValue.contains("Checkbox") {
switch button.identifier {
case serveBeerCheckbox.identifier:
// Do something with the Checkbox
serveBeer = (serveBeerCheckbox?.state == .on)
default:
// Another checkbox button
}
} else if identifier.rawValue.contains("RadioButton") {
switch button.identifier {
case headSize0RadioButton.identifier:
headSize = 0
case headSize1RadioButton.identifier:
headSize = 1
case headSize2RadioButton.identifier:
headSize = 2
default:
}
} // You could continue checking for different types of buttons
print("Serve beer? \(serveBeer ? "Sure!" : "Sorry, no.")")
if serveBeer {
switch headSize {
case 1:
print("With one inch of head.")
case 2:
print("With two inches of head!")
default:
print("Sorry, no head with your beer.")
}
}
}
}
As you can see, one could write a very generic method that can work on any type of UI element and use the rawValue of the identifier string with .contains() to isolate the type of element being worked with.
I have found using this approach allows me to initialize a UI with a lot of different elements pretty quickly and efficiently without having to recall tag numbers.
I have a controller which serves as a delegate to two scrollviews which are placed in view managed by aforementioned view controller.
To distinguish between two scroll views I'm trying to use switch statement (instead of simple pointer comparison with if statement). I have tagged both scroll views as 0 and 1 like this
NSUInteger const kFirstScrollView = 0;
NSUInteger const kSecondScrollView = 1;
When I try to use these constants in a switch statement, the compiler says that case statements are not constants.
switch (scrollView.tag) {
case kFirstScrollView: {
// do stuff
}
case kSecondScrollView: {
// do stuff
}
}
What am I doing wrong?
This can be solved through the use of an anonymous (though not necessarily so) enum type:
enum {
kFirstScrollView = 0,
kSecondScrollView = 1
};
switch (scrollView.tag) {
case kFirstScrollView: {
// do stuff
}
case kSecondScrollView: {
// do stuff
}
}
This will compile without errors.
This is because case statement requires constant expression. Now in C and thus in Obj-C making a variable const does not create a true constant. Thus you are getting this error. But if you use C++ or Obj-C++ then this will work.
Some more hint is available here and here.