UIKit

View Architecture

Every view has underlying Core Animation layer

• UIView – defines a rectangular region on the screen and handles the drawing and touch events
• CALayer – manages the backing store for the view and handles view-related animations

View Properties

							// Defines position of the view in it's parent
							var frame: CGRect
							// Defines bounding rectangle for view's content
							var bounds: CGRect
							// Array of all subviews contained in the view
							var subview: [UIView]
							// Access to underlying Core Animation
							var layer: CALayer
						

Views Stack

UIView Subclasses

UIScrollView

Allows to display content bigger than view's boundaries

UIControl

Conveys a particular action or intention to the app
through user interaction

Outlet

Connects storyboard item to the code

							@IBOutlet weak var myButton: UIButton!
						

Action

Connects event handler to a control

							@IBAction func buttonTouched(sender: UIButton) { }
						

Connections

List of all objects
connected to the UI element

Element must be removed from connections
when deleted

Auto Layout

Purpose

Auto Layout provides a set of constraints
to describe position and size of a view
in relation to its surrondings

Attributes

Every view has 9 Layout Attributes

Anatomy of Constraint

Every constraint describes relationship
between two attributes

Types of Constraints

• Alignment Constraint describes how views are positioned in relation to each other and to their container
• Pinning Constaraint describes view's intrinsic attributes and margins

Alignment Constraints

Pinning Constraints

Debugging Constraints

• Warnings can be resolved automatically by either fixing view, or modifing constraints
• Errors could only be resolwed by a programmer:
  • Unsatisfiable Layouts: your layout has no valid solution
  • Ambiguous Layouts: your layout has two or more possible solutions
  • Logical Errors: there is a bug in your layout logic

Stack View

Allows automatic alignment of contained views
for simplified layout

Intrinsic Content Size

• Content hugging pulls the view inward
  so that it fits snugly around the content
• Compression resistance pushes the view outward
  so that it does not clip the content

Constraints at Runtime

							// Creaye new constraint
							// myView.Leading = view.LeadingMargin * 1.0 + 0.0
							let constraint = NSLayoutConstraint(
								item: myView, attribute: .Leading,
								relatedBy: .Equal,
								toItem: view, attribute: .LeadingMargin,
								multiplier: 1.0, constant: 0.0)
							// Activate new constraint
							constraint.active = true
							// Recalculate view's dimentions
							myView.layoutIfNeeded()
							// Remove new constraint
							myView.removeConstraint(constraint)

						

Default Controllers

Navigation Controller

Navigation Bar

A navigation bar can display a left button, title, prompt string and right button(s)

Navigation in Storyboard

Editor → Embed In → Navigation Controller

Tab Bar Controller

Provides easy access to different views in an app

Each view can be a start of separate view stack

Table View Controller

Can be divided into sections

Each section contains
any number of cells

Able to present static or
dynamic content

Table View Cell

• In dynamic Table View
  Each prototype cell describes appearence of
  multiple cells in the table. Each prototype has a Reuse Identifier
• In static Table View
  Each cell added in Interface Builder describes its own content

Prototype Cells

Each prototype cell describes appearence of
multiple cells in the table

Each prototype cell has a Reuse Identifier

Default Cell Style

							// Returns the label used for the main textual content of the table cell
							var textLabel: UILabel?
							// Returns the secondary label of the table cell if one exists
							var detailTextLabel: UILabel?
							// Returns the image view of the table cell
							var imageView: UIImageView?
						

Table View Data Source

						override func tableView(tableView: UITableView,
							numberOfRowsInSection section: Int) -> Int {
							return 5
						}
						override func tableView(tableView: UITableView,
							cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
							let cell = tableView.dequeueReusableCellWithIdentifier("RobinTheMan",
								forIndexPath: indexPath)
							cell.textLabel.text = String(indexPath.row)
							return cell
						}
						

Collection View Controller

Collection View Cell

Handling Segues

Segue

A segue represents the transition from one scene
to the next scene

Segue Type

Show		Push on top of main stack
Show Detail		Push on top of detail stack
Present in Popover		Show in popover view
Present Modally		Show on top of current root view
Custom		Custom Segue

Identifier

Prepare for Segue

Perform Segue