Why Storyboards?

A visual tool for laying out multiple application views and the transitions between them.

• For the less technically inclined, Storyboards can be a great way to contribute to the project directly, e.g. by tweaking colors or layout constraints. However, this requires a working project setup and some time to learn the basics.
• Iteration is often faster since you can preview certain changes without building the project.
• In Xcode 6, custom fonts and UI elements are finally represented visually in Storyboards, giving you a much better idea of the final appearance while designing.
• Ease of use

A classic beginner’s mistake is to create one massive project-wide Storyboard. A Storyboard is a board with a story to tell. It shouldn't be used to mix unrelated stories into one big volume.

Project Structure

To keep all those hundreds of source files ending up in the same directory, it's a good idea to set up some folder structure depending on your architecture. For instance, you can use the following:

Classes

Application Delegate Category Constant Models Network Manager Shared Manager Utility Function View Controller

Views

StoryBoard.storyboard LaunchScreen.xib

Resources

Slices Fonts Sounds

First, create them as groups (little yellow "folders") within the group with your project's name in Xcode's Project Navigator. Then, for each of the groups, link them to an actual directory in your project path by opening their File Inspector on the right, hitting the little gray folder icon, and creating a new subfolder with the name of the group in your project directory.

CocoaPods

If you're planning on including external dependencies (e.g. third-party libraries) in your project, CocoaPods offers easy and fast integration. Install it like so:

sudo gem install cocoapods

To get started, move inside your iOS project folder and run

pod init

This creates a Podfile, which will hold all your dependencies in one place. After adding your dependencies to the Podfile, you run

pod install

to install the libraries and include them as part of a workspace which also holds your own project. It is generally recommended to commit the installed dependencies to your own repo, instead of relying on having each developer running pod install after a fresh checkout.

Note that from now on, you'll need to open the .xcworkspace file instead of .xcproject, or your code will not compile. The command

pod update

will update all pods to the newest versions permitted by the Podfile. You can use a wealth of operators to specify your exact version requirements.

Constants

The two most common ways of storing constants in Swift are:

Global constant

let someStringConstant = "someStringConstant"
// OR static
static let someStaticStringConstant = "someStaticStringConstant"

This has the advantage of being short. It’s just called in code like:

print(someStringConstant).

*Quick note: Globals are lazy — a.k.a. they will only be initialized when accessed the first time.

Struct (my former preferred method)

In my opinion the best way to deal with global constants is to create a Struct.

struct Constants {
    static let someNotification = "TEST"
}

Then, for example, call it like this in your code:

print(Constants.someNotification)

If you want a better organization I advise you to use segmented sub structs.

struct K {
    struct NotificationKey {
        static let Welcome = "kWelcomeNotif"
    }

    struct Path {
        static let Documents = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String
        static let Tmp = NSTemporaryDirectory()
    }
}

This method has the advantage of readability. The disadvantage of this method (and my personal hangup) is that these calls can get quite long.

When and where use constants : If a stored value in your code won’t change, always declare it as a constant with the let keyword. Use variables only for storing values that need to be able to change.

Event Patterns

These are the idiomatic ways for components to notify others about things:

• Delegation: (one-to-one) Apple uses this a lot (some would say, too much). Use when you want to communicate stuff back e.g. from a modal view.
• Callback blocks: (one-to-one) Allow for a more loose coupling, while keeping related code sections close to each other. Also scales better than delegation when there are many senders.
• Notification Center: (one-to-many) Possibly the most common way for objects to emit “events” to multiple observers. Very loose coupling — notifications can even be observed globally without reference to the dispatching object.
• Key-Value Observing (KVO): (one-to-many) Does not require the observed object to explicitly “emit events” as long as it is Key-Value Coding (KVC) compliant for the observed keys (properties). Usually not recommended due to its implicit nature and the cumbersome standard library API.

Assets

Asset catalogs are the best way to manage all your project's visual assets. They can hold both universal and device-specific (iPhone 4-inch, iPhone 4.7-inch, iPhone 5.8-inch, iPhone Retina, iPad, etc.) assets and will automatically serve the correct ones for a given name. Teaching your designer(s) how to add and commit things there (Xcode has its own built-in Git client) can save a lot of time that would otherwise be spent copying stuff from emails or other channels to the codebase. It also allows them to instantly try out their changes and iterate if needed.

An asset catalog can contain four types of images:

• App icons
• Launch images
• Images
• OS X icons

Asset catalog colors on Xcode 9 One of most exciting features on Xcode 9 is being able to add colors to an asset catalog, or as known as the .xcassets directory, alongside your images. This feature helps developers save time and avoid mistakes, by organizing project colors in a single location. Much cleaner!

• Adding colors to an asset catalog : Adding colors to an asset catalog might be hard to discover. After selecting your .xcassets directory in Xcode, press the plus button on the bottom left and select “New Color Set”.

Courtesy of : Zeplin Blog

• Using asset catalog colors in Storyboards : Using asset catalog colors in a Storyboard or an Interface Builder file is pretty straightforward. All color fields, including view background colors, label text colors, should display the colors you defined in the asset catalog under the “Named Colors” section.

• Using asset catalog colors in code : Using asset catalog colors in code is not so obvious, yet simple. Both UIColor on iOS and NSColor on macOS now have a convenience initializer in Swift to access these colors by name:

// iOS
let color = UIColor(named: "SillyBlue")

// macOS
let color = NSColor(named: "SillyBlue")

These methods are only available if you’re targeting iOS 11+ or macOS 10.13+, so you might need to stick to your existing color constants for a while.

Using Bitmap Images

Asset catalogs expose only the names of image sets, abstracting away the actual file names within the set. This nicely prevents asset name conflicts, as files such as button_large@2x.png are now namespaced inside their image sets. However, some discipline when naming assets can make life easier:

IconCheckmarkHighlighted.png // Universal, non-Retina
IconCheckmarkHighlighted@2x.png // Universal @2x, Retina
IconCheckmarkHighlighted@3x.png // Universal @3x, Retina (@3x is only on iPhone as of now!)
IconCheckmarkHighlighted~iphone.png // iPhone, non-Retina
IconCheckmarkHighlighted@2x~iphone.png // iPhone, Retina
IconCheckmarkHighlighted-568h@2x~iphone.png // iPhone, Retina, 4-inch
IconCheckmarkHighlighted~ipad.png // iPad, non-Retina
IconCheckmarkHighlighted@2x~ipad.png // iPad, Retina

The modifiers -568h, @2x, ~iphone and ~ipad are not required per se, but having them in the file name when dragging the file to an image set will automatically place them in the right "slot", thereby preventing assignment mistakes that can be hard to hunt down.

`Developers work with point values, so it is important to understand the difference with pixels. When the iPhone was first introduced, the two units were the same: 1pt equals 1px. Then when retina screens came along, 1pt became 2px. So think of points as the values in the or