Nsdictionaryofvariablebindings Swift Equivalent

convert objc to swift regarding NSDictionaryOfVariableBindings

You just take every view that is listed in NSDictionaryOfVariableBindings and create a usual swift dictionary containing this view with the variable name as a key.

Example:

NSDictionaryOfVariableBindings(view1, view2, view3)

will become

["view1" : view1, "view2" : view2, "view3" : view3]

So

NSDictionary *views = NSDictionaryOfVariableBindings(subview);

will become

let views = ["subview" : subview]

Objective C equivalent of Swift addConstraints?

NSDictionaryOfVariableBindings produces variable bindings that match your Objective-C variable names. So you need to write the constraint as

[self addConstraints:[NSLayoutConstraint 
constraintsWithVisualFormat:@"H:|-16-[thumbnailImageView]-16-|" 
options:0 
metrics:nil 
views:NSDictionaryOfVariableBindings(thumbnailImageView)]];

Or you just skip NSDictionaryOfVairableDBindings and use:

[self addConstraints:[NSLayoutConstraint 
constraintsWithVisualFormat:@"H:|-16-[v0]-16-|" 
options:0 
metrics:nil 
views:@{ @"v0" : thumbnailImageView } ];

which is a bit more like the Swift version. (Don't have compiler handy just at the moment so might be some small syntax errors in the second part. Will check ASAP).

convert objc to swift regarding NSDictionaryOfVariableBindings

You just take every view that is listed in NSDictionaryOfVariableBindings and create a usual swift dictionary containing this view with the variable name as a key.

Example:

NSDictionaryOfVariableBindings(view1, view2, view3)

will become

["view1" : view1, "view2" : view2, "view3" : view3]

So

NSDictionary *views = NSDictionaryOfVariableBindings(subview);

will become

let views = ["subview" : subview]

Width and Height Equal to its superView using autolayout programmatically?

I'm not sure if this is the most efficient way to do it, but it works..

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
button.translatesAutoresizingMaskIntoConstraints = NO;
// initialize

[coverForScrolView addSubview:button];

NSLayoutConstraint *width =[NSLayoutConstraint
                                    constraintWithItem:button
                                    attribute:NSLayoutAttributeWidth
                                    relatedBy:0
                                    toItem:coverForScrolView
                                    attribute:NSLayoutAttributeWidth
                                    multiplier:1.0
                                    constant:0];
NSLayoutConstraint *height =[NSLayoutConstraint
                                     constraintWithItem:button
                                     attribute:NSLayoutAttributeHeight
                                     relatedBy:0
                                     toItem:coverForScrolView
                                     attribute:NSLayoutAttributeHeight
                                     multiplier:1.0
                                     constant:0];
NSLayoutConstraint *top = [NSLayoutConstraint
                                   constraintWithItem:button
                                   attribute:NSLayoutAttributeTop
                                   relatedBy:NSLayoutRelationEqual
                                   toItem:coverForScrolView
                                   attribute:NSLayoutAttributeTop
                                   multiplier:1.0f
                                   constant:0.f];
NSLayoutConstraint *leading = [NSLayoutConstraint
                                       constraintWithItem:button
                                       attribute:NSLayoutAttributeLeading
                                       relatedBy:NSLayoutRelationEqual
                                       toItem:coverForScrolView
                                       attribute:NSLayoutAttributeLeading
                                       multiplier:1.0f
                                       constant:0.f];
[coverForScrolView addConstraint:width];
[coverForScrolView addConstraint:height];
[coverForScrolView addConstraint:top];
[coverForScrolView addConstraint:leading];

How to use Visual Format Language to set constraints in Swift?

Visual Format Language allows you to apply programmatic constraints using visual syntax strings. As per the Apples Documentation, the idea is the text visually matches the layout.

Let's break down the syntax part for better understanding:

H: (Horizontal) //horizontal direction
V: (Vertical) //vertical direction
| (pipe) //superview
- (dash) //standard spacing (generally 8 points)
[] (brackets) //name of the object (uilabel, unbutton, uiview, etc.)
() (parentheses) //size of the object
== equal widths //can be omitted
-16- non standard spacing (16 points)
<= less than or equal to
>= greater than or equal to
@250 priority of the constraint //can have any value between 0 and 1000

Now, in order to apply constraint to a view using visual format language, fir we need to make translatesAutoresizingMaskIntoConstraints false for the view, on which we are going to apply constraints:

imageView.translatesAutoresizingMaskIntoConstraints = false

then we need to prepare a dictionary for all the views, which are to be used in VFL like:

let viewDictionary = NSDictionaryOfVariableBindings(imageView)

then make horizontal and vertical constraints using Visual Format String as per the rules explained above:

let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-[imageView]-|", options: NSLayoutConstraint.FormatOptions(), metrics: nil, views: viewsDictionary)
let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:|-[imageView(100)]-|", options: NSLayoutConstraint.FormatOptions(), metrics: nil, views: viewsDictionary)

Now, add these constants to your superview like:

view.addConstraints(horizontalConstraints)
view.addConstarints(verticalConstraints)

PS: If you want to make view's width/height dynamic, you need to create a matrics dictionary, pass it in metrics: instead of setting it nil and then using the appropriate keyname for the value. For example:

let metricDict = ["viewHeight":300]
let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:|-[imageView(viewHeight)]-|", options: NSLayoutConstraint.FormatOptions(), metrics: metricDict, views: viewsDictionary)

Custom UIView above UITableView (when user pulls to refresh)

The answer is: use AutoLayout.

Storyboard

You can add all the constraints you need from the storyboard

XIB

If loading a UIView programmatically, you can also add NSLayoutConstraint programmatically. They are guaranteed to work in landscape mode.

...but I can't get them working...

Look at https://stackoverflow.com/a/18759148/218152 and add constraints for refreshBackgroundView height. To pin it:

// Add constraints to fit to superview, below the nav bar
UIView * hintView = self.refreshBackgroundView;
[hintView setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.tableView addConstraints:[NSLayoutConstraint
                               constraintsWithVisualFormat:@"H:|-0-[hintView]-0-|"
                               options:NSLayoutFormatDirectionLeadingToTrailing
                               metrics:nil
                               views:NSDictionaryOfVariableBindings(hintView)]];

id<UILayoutSupport> guide = self.topLayoutGuide;
[self.tableView addConstraints:[NSLayoutConstraint
                               constraintsWithVisualFormat:@"V:|[guide]-0-[hintView]-0-|"
                               options:NSLayoutFormatDirectionLeadingToTrailing
                               metrics:nil
                               views:NSDictionaryOfVariableBindings(hintView, guide)]];

UIRefreshControl

You should really use a UIRefreshControl for long term compatibility.

Add Vertical Spacing programmatically in swift

Let suppose your UIImageView is added in the top as you put in your image above, then you can add constraints programmatically like in the following way:

override func viewDidLoad() {
    super.viewDidLoad()

    // assuming here you have added the self.imageView to the main view and it was declared before. 
    self.imageView.setTranslatesAutoresizingMaskIntoConstraints(false)

   // create the constraints with the constant value you want.
   var verticalSpace = NSLayoutConstraint(item: self.imageView, attribute: .Bottom, relatedBy: .Equal, toItem: self.button, attribute: .Bottom, multiplier: 1, constant: 50)

  // activate the constraints
  NSLayoutConstraint.activateConstraints([verticalSpace])
}

In the above code I only put the vertical space constraints, you need to set the necessary constraints to avoid warnings about it.

There are several ways of adding constraint programmatically you can read more in this very nice answer SWIFT | Adding constraints programmatically.

I hope this help you.

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