This is about iOS coding style convention.

Naming Convention

Object Name

Object name starts with MN as Mapsted Navigation.

Property Name

For private class property, starts with _ followed by a lower camel case character. For example:

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private var buildingData: MNBuildingData 	// [Not Preferred]
private var _buildingData: MNBuildingData 	// [Preferred]

Enums

Enums should always use upper camel case. Case for enum uses lower camel case. For example:

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enum LayerType {
	case building, property
}

Swift Coding Style

Constants vs Variable

Constants are defined using let keyword. Always use let instead of var if the value will not change. Tips: A good technique is to define everything using let and only change it to var if the compiler complains.

Optional

Only define optional variable where a nil value is acceptable. Don’t use ! unless for @IBOutlet. Avoid naming optional variables to something like optionalValue or stringNilable

Spacing

Indent using 2 space rather than tabs to conserve space and help prevent line wrapping. Make sure to set this in Xcode.

For method {} brackets or if/else/switch/while, always open on the same line as the statement but close on a new line.

Preferred:

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if bool {
  // do something
} else {
  // do something
}

Not preferred:

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if bool
{
  // do something
} else
{
  // do something else
}

Use of Self

Use self. only when required by the compiler. (In @escaping closures, or in initializers to disambiguate properties from arguments). In other words, if it compiles without self then omit it.

Switch

Switch should cover all the cases if necessary, do not use default unless really needed.

Access Control

Always using private if the function does not access from outside the class. Only using fileprivate, open, public, internal when you require a full access control specification. Always using an access control specifier before any function, class properties unless it’s a function coming from coca-touch or any third-party libraries. The access control specifier should always be the first one.

Preferred:

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class A {
  private dynamic lazy var b = B()
  private func calc() {
    // do something
  }
}

Not Preferred:

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class A {
  lazy dynamic private var b = B() // specifier order matters
  func calc() { // missing access control
    // do something
  }
}

Objective-C Coding Style

For Objective-C coding convention, we mostly adapt to apple’s coding guidelines for cocoa and adding some our own changes. Apple’s coding guidelines can be found in Introduction to Coding Guidelines for Cocoa. Below will include anything important in that guideline as well.

Defining Methods

Naming Methods

Here is how you want to define methods, please notice how I use space in this example.

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- (type)doIt;
- (type)doItWithA:(type)a;
- (type)doItWithA:(type)a b:(type)b;

Here is a list of rules for naming methods.

  1. Start the name with a lowercase letter and capitalize the first letter of embedded words.
  2. For methods that represents actions an object takes, start the name with a verb:
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    - (void)invokeWithTarget:(id)target;
    - (void)selectTabViewItem:(NSTabViewItem *)tabViewItem
  3. If the method returns an attribute of the receiver, name the method after the attribute. The use of the “get” is unnecessary, unless one or more values are returned indirectly.
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    - (NSSize)cellSize 		//right
    - (NSSize)calcCellSize 	//wrong
    - (NSSize)getCellSize		//wrong
  4. Use keywords before all arguments
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    - (void)sendAction:(SEL)aSelector toObject:(id)anObject forAllCells:(BOOL)flag;	//right
    - (void)sendAction:(SEL)aSelector anObject:(id)anObject flag:(BOOL)flag; 		//not good
    - (void)sendAction:(SEL)aSelector :(id)anObject :(BOOL)flag; 					//wrong
  5. Make the word before the argument describe the argument
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    - (id)viewWithTag:(NSInteger)aTag; 	//right
    - (id)taggedView:(int)aTag; 			//wrong

Accessor Methods

Accessor methods are methods that set and return the value of a property of an object. They have certain recommended forms, depending on how the property is expressed.

  1. If the property is expressed as a noun, the format is:
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    - (type)noun;
    - (void)setNoun:(NSString *)aNoun;

    // For example:
    - (NSString *)title;
    - (void)setTitle:(NSString *)aTitle;
  2. If the property is expressed as an adjective, the format is:
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    - (BOOL)isAdjective;
    - (void)setAdjective:(BOOL)flag;

    // For example:
    - (BOOL)isEditable;
    - (void)setEditable:(BOOL)flag;
  3. If the property is expressed as a verb, the format is:
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    - (BOOL)verbObject;
    - (void)setVerbObject:(BOOL)flag;

    // For example:
    - (BOOL)showsAlpha;
    - (void)setShowsAlpha:(BOOL)flag;
    The verb should be in the simple present tense. You may use modal verbs (verbs preceded by “can”, “should”, “will” and so on) to clarify meaning, but don’t use “do” or “does”. For example:
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    - (void)setCanHide:(BOOL)flag; 				//right
    - (BOOL)canHide; 								//right
    - (void)setShouldCloseDocument:(BOOL)flag;	//right
    - (BOOL)shouldCloseDocument;					//right
    - (void)setDoesAcceptGlyphInfo:(BOOL)flag;	//wrong
    - (BOOL)doesAcceptGlyphInfo;					//wrong
  4. Use “get” only for methods that return objects and values indirectly. You should use this form for methods only when multiple items need to be returned. For example:
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    - (void)getLineDash:(float *)pattern count:(int *)count phase:(float *)phase;