Use of square brackets [] for objective-C understanding

1. It is used to notify an object of what to do, that is, the notification object executes an action.

1.1. in objective-C, square brackets also have other meanings: they are used to notify an object of what to do.

For example:

[Shape draw];// This statement indicates that the shape of the notification object is used to execute the draw action. For example, a rectangle is used to draw a rectangle.

1.2. In objective-C, the notification object performs an operation, which is called sending a message.

For example:

[Shape draw];// Send a draw message to the object shape.

2. Create a new object

To create a new object, we need to send a new message to the corresponding class.

After receiving and processing the new message, this class will get a new object instance that can be used.

For example:

Id shape [3];

Shape [0] = [circle new];// Send a new message to the Circle class. A new object is created and assigned to shape [0].

3. Send messages to the superclass in the class

3.1 for example:

@ Interface circle: Shape

@ End // circle

@ Implementation circle

-(Void) setfillcolor :( shapecolor) c {

If (C = kredcolor ){

C= Kgreencolor;

}

[Super setfillcolor: C];
// Send a message to the superclass shape. The superclass will execute its setfillcolor method.

}

@ End // circle

3.2 for example:

Self = [Super init];// Enables the superclass nsobject to complete its initialization. And if a new object is returned,

// Update self.