40 Matching questions
- leading (+) sign
- leading (-) sign
- Create an object to store a fraction
- The @implementation section in detail
- Display the value of myFraction
- Set the value of your fraction
- Rules for forming names
- An instance of a car
- Create the object (ask the factory to build a car). This zeros out all of the object's instance variables.
- The @implementation section
- The @ interface section details
- Fraction *myFraction
- Allocating a new object (using alloc)
- A method that takes an argument
- When a method name ends with a colon, it means that it is expecting to see an argument.
- Return Values
- Applying methods to classes or instances
- Three-line sequence (final shorthand)
- The program section
- instance methods
- Factory or class methods
- The program section in detail
- The @interface section
- The ultimate goal for objects
- Each time a new car is manufactured, a new instance from the class of car is created, and each instance of the car is referred to as an object.
- The @implementation section general format
- A value is returned from a method using the return statement.
- Two-line sequence of allocating a new instance of a class and initializing it
- Initialize the object
- General format for the @interface section
- The name of the class
- Applying the same methods to different objects is one of the key concepts of object-oriented programming
- Specifying an integer argument
- How to get a new car
- You can also declare the instance variables for a class in the interface section. This is considered a better way to define a class.
- a automatically generates methods for you
- b A thing.
- c [ ClassOrInstance method ];
[ receiver message ];
- d Note
- e 1. You have to define where the class came from when you define a new class. That is, you have to name it's parent class.
2. You need to define the type of operations, or methods, that can be used when working with objects from this class.
3. You also need to list items known as properties
- f - (int) returns an integer
- (void) returns no value
- (double) returns a decimal
Tells the program what type of value the method returns
- g - (void) setNumerator: (int) n;
- h note
- i Make your programs easier to write, code, and maintain.
- j Methods that apply only to your car
- k Fraction *myFraction;
- l - (void) setNumerator: (int) n;
Integer arguments are indicated by the (int) in front of the argument name.
- m @interface NewClassName: ParentClassName
- n [ yourCar setSpeed: 55 ];
set the speed to 55 mph
- o // Set fraction to 1/3
[myFraction setNumerator: 1];
[myFraction setDenominator: 3];
The first message statement sends the setNumerator: message to myFraction. The argument that is supplied is the value 1.
Inside the setNumerator: method, the passed value of 1 is stored inside the variable n. The single program line in that method effectively stores that value in the instance variable numerator.
- p yourCar = [ Car new ];
You send a NEW message to the car class (the receiver of the message) asking it to give you a new car. The resulting object (which represents your unique car) is then stored in the variable yourCar. From now on, yourCar can be used to refer to your instance of the car.
- q An action that is performed on an instance of a class or to the class itself
- r Describes the data (the instance variables that objects from a class will store) and contains the actual code that implements the methods declared in the interface section.
- s indicates an instance method
- t @implementation NewClassName
NewClassName is the same name that was used for the class in the @interface section.
The memberDeclarations section specifies what types of data are stored in your instance of the class. It is enclosed inside its own curly braces
The members declared in this section are known as instance variables. Each time you create a new object, a new and unique set of instance variables are also created.
The methodDefinition part of the @implementation section contains the code for each method specified in the @interface section.
Each method starts by identifying the type of the method (class or instance; + or -), its return type, and its arguments and their types. Instead of the line ending in a semicolon, the code for the method follows, enclosed in a set of curly braces.
- u You have to describe the data that members of the class will contain. These members are called instance variables. You declare the methods in the @interface section and then you define them in the @implementation section.
- v The method new is an example of a class method because you have to go to the factory to get a new Car.
- w Describes the class and its methods
- x myFraction = [[Fraction alloc] init]
- y myFaction = [myFraction init];
Note that you are not sending the init method to a class, you are sending it to the instance of the class
- z object oriented programming example
- aa NSLog (@"The value of myFraction is: ");
invokes the print method
- ab indicates a class method
- ac A unique occurrence of a class
- ad They must begin with a letter or underscore (_) and they can be followed by any combination of letters (uppercase or lowercase), underscores, or the digits 0 through 9.
- ae Fraction *myFraction = [[Fraction alloc] init]
- af Note
- ag Your particular car
- ah enough space is reserved in memory to store the object's data, which includes space for its instance variables, and a little more. The location where the data is stored is returned by the alloc routine, and assigned to myFraction.
- ai The asterisk represents a reference (or pointer) to a object. The variable myFraction doesn't actually store the fraction's data. Instead it stores a reference - which is a memory address - indicating where the object's data is located in memory. You can think of it as an empty box.
- aj myFraction = [Fraction alloc];
- ak Applying a method to an object will affect the state of that object
- al car
- am This section contains the code to solve your particular problem, which can be spread out across many files. Somewhere you must have a routine called main. That's where your program begins execution.
- an Contains the program code to carry out the intended purpose of the program.