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Swift Style Guide.md

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Swift code guidelines

1. Code Formatting

1.1 Use 4 spaces to indent lines.

1.2. Trim trailing whitespaces (Xcode -> Preferences -> Text Editing -> Automatically trim trailing whitespace + Including whitespace-only lines).

1.3. No space before colon and one space after it. Exceptions are the ternary operator ? :, empty dictionary [:] and #selector syntax addTarget(_:action:).

Preferred:

let fooDictionary: [String: Any]
let testValue: Double
func handle(response: Response)

1.4. No semicolons at the end of line.

1.5. Use Xcode indentation (Command-A, Control-I).

2. Naming

2.1. Use CamelCase for types and protocols; lowerCamelCase for everything else (function, method, property, constant, variable, argument names, enum case).

2.2. Start factory methods with word make.

2.3. Choose clarity over brevity.

2.4. Name booleans like isAuthenticated instead of authenticated.

2.5. Name function parameters where it is appropriate.

Preferred:

func move(from start: Point, to end: Point)
func makeRequest(withTimeout timeout: TimeInterval, headers: [String: String])
func handleEvents(_ events: [Event])
func compare(_ firstDate: Date, _ secondDate: Date) -> DateResult

Not preferred:

func move(_ start: Point, _ end: Point)
func makeRequest(_ timeout: TimeInterval, dict: [String: String])
func handleEvents(events: [Event])
func compare(firstDate: Date, secondDate: Date) -> DateResult

2.6. The protocols that describe what something is should read as nouns (e.g. Iterator, Collection).

2.7. The protocols that describe a capability should end in -able or -ible (e.g. Comparable, Hashable, Codable)

3. Coding style

3.1. Avoid writing self. unless it is required by compiler or for readability purposes.

3.2. Use let over var whenever possible.

3.3. Mark types, functions, properties, constants, variables with private where it is applicable.

3.4. Use private(set) for properties to make them readonly (e.g. IBOutlet).

3.5. Avoid internal access modifier keyword since it is declared by default.

3.6. Use final when a class must not (or is not designed to) be inherited (e.g. singleton).

3.7. Omit unnecessary parentheses.

Preferred:

if name == "okta" { ... }
switch tokenType { ... }
let formattedTokens = tokens.map { $0 + "\\" }
tokens.forEach { number in print(number) }

Not preferred:

if (name == "okta") { ... }
switch (tokenType) { ... }
let formattedTokens = tokens.map() { $0 + "\\" }
tokens.forEach { (number) in print(number) }

3.8. Use compiler inferred context.

Preferred:

view.backgroundColor = .red
let customView = UIView(frame: .zero)
let selector = #selector(viewDidLoad)
let message = "Hello Okta!"

Not preferred:

view.backgroundColor = UIColor.red
let customView = UIView(frame: CGRect.zero)
let selector = #selector(MyViewController.viewDidLoad)
let message: String = "Hello Okta!"

3.9. Name unused closure parameters as underscores _.

3.10. Avoid nested if/else statements. Use Happy Path rule.

Preferred:

func message(from response: Response) -> String? {
  guard let context = response.context else {
    return nil
  }

  guard context.isAuthenticated else {
    logOut()
    return nil
  }

  return "User is authenticated"
}

Not preferred:

func message(from response: Response) -> String? {
  if let context = response.context {
      if context.isAuthenticated {
        return "User is authenticated" 
      } else {
        logOut()
        return nil 
      }
  } else {
    return nil
  }
}

3.11. Use trailing closure syntax when single closure parameter.

Preferred:

sendRequest(request) { response, error in
 ...
}

Not Preferred:

sendRequest(request, completion: { response, error in
 ...
})

3.12. Use multi-line string literal.

Preferred:

let testOktaToken = """
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. \
    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, \
    when an unknown printer took a galley of type and scrambled it to make \
    a type specimen book.
    """

3.13. Use multi-line guard statements.

Preferred:

guard let user = response["user"] as? User,
      let username = user.username
else {
    return
}

Not preferred:

guard let user = response["user"] as? User, let username = user.username else {
    return
}

guard let user = response["user"] as? User,
      let username = user.username else {
    return
}

3.14. Use XCTUnwrap instead of forced unwrapping in tests.

4. Don'ts

4.1. Don't use fatalError or precondition. Prefer assert if it is recoverable case. If not, handle it in proper way.

4.2. Avoid implicit unwrapping (!), as this will cause a crash if a value is nil. Unwrap using guard let or if let and handle error cases in code as appropriate (e.g. logging, return an error etc.).

4.3. Don't leave unused or dead code.

4.3. Don't leave commented out code.

4.4. Don't use DispatchQueue.main.asyncAfter to fix the issues via delays.

4.5. Don't include your name in source code. Use the common copyright header.

/*
 * Copyright (c) 2021-Present, Okta, Inc. and/or its affiliates. All rights reserved.
 * The Okta software accompanied by this notice is provided pursuant to the Apache License, Version 2.0 (the "License.")
 *
 * You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *
 * See the License for the specific language governing permissions and limitations under the License.
 */

Contribution

The style guide is not set in stone. This document should evolve along with Swift. So feel free to add new items.