Go on. Explore!

lvl 0 • 0 xp

lvl 1

Home Market Decks Interests

Objective-C Syntax

memorize.ai (lvl 286)

(0)

32 cards

()

Section 1

Preview this deck

Creating a Class instance

Front

1 / 32

iOS Dev

0.0

0 reviews

5			0
4			0
3			0
2			0
1			0

Active users

All-time users

Favorites

Last updated

4 years ago

Date created

Mar 1, 2020

Cards (32)

Section 1

(32 cards)

Creating a Class instance

Front

ClassName *myClass = [[ClassName alloc] init];

Back

designated initializer

Front

prevents initialization loops with using inheritance. This is the initilizer that a child class should use to initilize its superclass instance variables, it is defined in the documentation of the class

Back

class implementation

Front

// implementaitons are stored in .m files // add private methods to implementation file #import "ClassInterface.h" @implementation className // no superclass here // implementation of pubic and private mentods @end

Back

Instantiation

Front

Creating an Object - objects can be created manually - or they can be created by other objects - "most of the objects you get by passing other objects"

Back

pointers and nil

Front

Classes are always on the heap in Objective C when a class pointer is defined it is set to nil if you pass a method to a nil object NOTHING HAPPENS, this is an error in some languages.

Back

for loop, while loop, switch

Front

same as C++ while loop has continue; // just breaks out of that cycle

Back

id

Front

a very important generic class, it is similar to void* but has useful methods associated on top of it. It can hold the pointer of any class.

Back

Class Methods

Front

// prototype + (returnType)methodName; //Calling a class method [ClassName method:arg] //Can get the class of an object and call a class method as follows [[instanceName class] classMethod]; // Class methods are typically used to get information about the class

Back

Relational Operators

Front

Same as C++ <, >, >=, <=, !=, ==

Back

self

Front

pointer to the object calling the method (like this) use it whenever you are manipulating an instance variable, it helps with code readability.

Back

main syntax

Front

int main(int argc, const char* argv[]){ //code return 0; // if sucessful }

Back

private methods in implementation file

Front

// at the top of the implementation add an interface @interface ClassName() // don't for get the () and no Superclass here // declaration of private methods here (as needed) @end

Back

Dynamic Binding

Front

in Objective-C the decision of what code is ran happens entirely at runtime. You can assign id to any class and access the classes methods even though the class is an id. The compiler assumes you know what you are doing if you are sending a message to an id. example: id obj = ....; [obj shoot]; //will compile, even if the object that obj was originally assigned to // does not contain a method called shoot

Back

class interfaces

Front

// interfaces are stored in .h files and have the following syntax #import "Superclass.h" // if the class has a superclass @interface ClassName : Superclass // Declare methods hear @end

Back

standard libraries

Front

Found in <Foundation/Foundation.h> i.e. #import <Foundation/Foundation.h> standard liberties are in <> and other headers are in ""

Back

method implementation

Front

- (returnType)functionNameA:(Arg1Type)arg1Name functionNameB:(Arg2Type)arg2Name { // put the code here to do the function } // no semicolon // it is all on one line this time

Back

Logical Operators

Front

Same as C++ &&, ||, !

Back

Introspection

Front

When id is used with an array to store many objects of different types.

Back

Conditional Operands

Front

variable = (condition) ? AssignValue1: AssignValue2; // if the variable is equal to the condition then AssignValue1 is // is used if not then AssignValue2 is used.

Back

method prototype syntax

Front

// it includes the - - (returnType)functionNameA:(Arg1Type)arg1Name functionNameB:(Arg2Type)arg2Name; // can all be on one line // try to line up the colons // the full name of the method is fuctionNameA:FunctionNameB: // See the following example - (void)orbitPlanet:(Plant *)aPlanet atAltitude:(double)km; // the name of this function is orbitPlanet:atAltitude:

Back

@synthesize

Front

// implements both the setter and getter for a @property // AND creates some storage to hold the value of the instance variable @synthesize nameOfProperty = _nameOfproperty; // this is the name of where the value is stored // if not the name will be nameOfProperty // apparently we always want to use = with @synthesize // to do more, synthesize only implemets the setters and // getters the you do not

Back

arithmetic and type casting

Front

same a C++ i.e. int Number = (int)(3.14*42.3);

Back

standard init implementation

Front

@implementation MyObject - (id)int { self = [super init]; //call supercalss initilizer if(self){ // initilize class here } return self; } @end all other initializers should call the designated initializer

Back

Setting and Getting

Front

// methods used to set and get a primitive data type // a simple method used to set a value, the implemention just sets ValueA to NewValueA - (void)setValueA:(double)NewValueA; // a get method simple returns the value - (double) ValueA; // @property is used to make this easier

Back

Creating an object from scratch

Front

-alloc is a class method of NSObject that allocates space in the heap large enough to hold all of the instance variables of the class that receives a message. -the instance variable will be initillally set to zero, if you want the to be otherwise use the init method to set the values. [[MyClass alloc] init] will do the job

Back

Calling a method

Front

[classPointer method]; or classPointer.Method // equivalent to classPointer->Method in C++ the compiler knows if you are calling a setter or a getter

Back

@property

Front

//declares a setter and a getter for a property //syntax @property (nonatomic) double nameOfProperty; // this makes the setNameOfProperty and nameOfProperty methods // nonatomic makes the property thread safe // notice that the property name starts with a lowercase // but the setter have a uppercase name // if you create a class property use strong for memory management @property (nonatomic, strong) ClassName *nameOfInstance;

Back

NSObject

Front

All objects inherited from NSObject, some useful methods are: isKindOfClass; //tells you if the class is of class(inheritance included) isMemberOfClass; // inheritance not included responds ToSelector: //returns weather an object responds to a given method // must use selectors with these objects

Back

selector

Front

a special object used testing objects i.e. using NSObject methods @selector() turns the name of a method into a selector example: @selector(shoot:Atpostion:) SEL shootSelector = @selector(shoot:); //SEL is a typedef that holds a selector.

Back

initializer

Front

(id)init; or (id)initWithProperty:(double)property; this is like the C++ constructor, most classes should implement init sensibly, you can have as many inits as you like using initWithProperty, this is similar to a constructor with arguments

Back

public and Private

Front

in objective C, anything that is in the .h (interface) file is public and anything that is in the .m (implementation) file is private

Back

#import

Front

Similar to #include, however takes care of redundancy (i.e. no #ifndef)

Back