Object

Object-Oriented Programming defines an object as “any entity that has a defined boundary.” An object has the following −

• State − Describes the object. The fields of a class represent the object’s state.
• Behavior − Describes what an object can do.
• Identity − A unique value that distinguishes an object from a set of similar other objects. Two or more objects can share the state and behavior but not the identity.

The period operator (.) is used in conjunction with the object to access a class’ data members.

Example

Dart represents data in the form of objects. Every class in Dart extends the Object class. Given below is a simple example of creating and using an object.

Live Demo

class Student { 
   void test_method() { 
      print("This is a  test method"); 
   } 
   
   void test_method1() { 
      print("This is a  test method1"); 
   } 
}  
void main()    { 
   Student s1 = new Student(); 
   s1.test_method(); 
   s1.test_method1(); 
}

It should produce the following output −

This is a test method 
This is a test method1

The Cascade operator (..)

The above example invokes the methods in the class. However, every time a function is called, a reference to the object is required. The cascade operator can be used as a shorthand in cases where there is a sequence of invocations.

The cascade ( .. ) operator can be used to issue a sequence of calls via an object. The above example can be rewritten in the following manner.

Live Demo

class Student { 
   void test_method() { 
      print("This is a  test method"); 
   } 
   
   void test_method1() { 
      print("This is a  test method1"); 
   } 
}  
void main() { 
   new Student() 
   ..test_method() 
   ..test_method1(); 
}

It should produce the following output −

This is a test method 
This is a test method1

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The toString() method

This function returns a string representation of an object. Take a look at the following example to understand how to use the toString method.

Live Demo

void main() { 
   int n = 12; 
   print(n.toString()); 
} 

It should produce the following output −

12