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Hello everyone.



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So in the last radio we discussed about copy constructor.



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So in this video we will learn about copy assignment operator and destructor.



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Okay so let's start with the copy assignment operator



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so let us take an example.



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Let's create an object first.



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So student S1 ages 10 all numbers and we have another object.



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We have another student as to ages 20.



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And rule number is 200 so in this case and in this case in both the cases betterment tries to construct



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it will be called so betterment based constructor is being getting called.



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So what is this an add to the effect of this line is very simple.



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Ages 10.



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Rule number is hundred.



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This is S1 and the effect of this line is also very simple.



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Age will be 20 and rule number will be 200.



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Now let's see what is our aim.



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So our aim is very simple what I want to do I want to copy the value of S1 into S2.



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Okay.



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I want to copy the value of S1 into S2.



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So each will become pen and roll number will become hundred so after creating that object I want to



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copy the value of S1 into S2.



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So the one simple way to do this is with the help of copy constructor



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so after creating the object can I call copy constructor.



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No see the objects are already being created the objects are already created.



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So what I want is after creating the object I am copying the values of one object to enter object so



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after creating the object can I call copy constructor.



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The answer is no we cannot call copy constructor because we know for one object constructor is called



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only once and that too at the time of creation of the object.



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And for S2 parametric constructor has already been called.



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Okay so what we have to do we have to copy the value explicitly so copy constructor will not work here.



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We have to copy the value explicitly so for copying the value exquisitely we have to write two lines



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one for copying the H and therefore copying the elements of our copying the age ages a private field.



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So what we have to do we will use public function get principal function so as to not set age then but



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really bad amateur will be as Ondaatje good age



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and since the roll number is public so we can access public we can access public methods outside the



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class so as to not remember it is s on daughter number.



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Now the point is we do not need to write these two lines.



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We do not need to write these two lines explicitly because we have an operator which will do our work



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and that operator is called a copy assignment operator net operator is called copy assignment operator



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so instead of writing these two lines I will write just one simple line as two equals S1 and that's



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all as two equals S1.



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So what do the effect of this line this line will say copy all the values of S1 into S2 copy all the



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values of s 1 and 2 S2 and this equal operator is called copy assignment operator Okay so what is the



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difference between copy constructor and copy assignment operator.



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So there are differences very simple copy constructor what it does is it creates it creates the copy



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at the time of creation of the object whereas word copy assignment operator does is copy something the



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operator will be useful when both the objects are already created in the memory and then we have to



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copy the values.



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Okay so copy constructor Create the copy at the time of creation of the object and copy assignment operator



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is used when both objects are already present in the memory and then you have to copy their values.



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Okay.



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So basically they do the same work there are the same book but like they work differently.



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Okay so copy constructor will be called at the time of creation of the object to create copy or for



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their object and copy assignment operator is useful when two objects are already present in the memory.



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And then you have to copy the values.



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Okay so enough of to read let's seeing or how this will look like.



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So first Heller does create two objects so that I can use copy as an interpreter so as to render S1.



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Let's say that ages 10 and the rule number is.



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Hundred and let us create an other object student as to age is twenty and Roland Burris 200.



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So what we have to do is one simple thing as two equals S1.



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Okay so copy assignment operator is used here.



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So copy assignment operator is also given us by the class as soon as we create the class copy assignment



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operator as well to created.



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Okay so what if we have a dynamic object then then within this index.



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So to the industry is new student is just today and rule number is tendered



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so this index will be quite similar status t is S1 copy the value of S1 and do S3 and similarly copy



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the value of S3 and do as to Okay so that Sol



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so this is how copy construct deadlocks Okay so copy the value of S1 and do as to copy the value of



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S1 into history and then copy the value of S3 and do S2 and this operator is called copy assignment



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operator so that's all for copy assignment operator we can create our own copy assignment operator also



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but we will do it in the next to read use in the videos later on.



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Okay so now now let us talk about destructor what is a destructor.



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What is the purpose of district band what are the properties of restricted.



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So as the name suggest what district devils do will be allocate the memory of the object it the allocates



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memory of the object delegates memory of objects.



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There are some properties of destructor for example it will have the same name as class name same name



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as class name no return type



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and it will not take any argument so annoying but I argument nine put barometers



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so if you remember these three are also the property of the default constructor.



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Default Constructor also put it is all these three properties.



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So how can we differentiate between destructor and default constructor.



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So what we will do we will use a special symbol called Taylor.



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Okay.



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So we will use the special symbolic like Delta to thus index the structure for Destructor is very similar.



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To the constructor.



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Student No input barometer and no return type.



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So this is the structure of.



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This is the structure ofa destructor.



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Okay.



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And the structure for default constructed we already know no return type 9 but argument nothing.



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Okay.



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So this is the structure of the default constructor so Destructor is automatically created as we create



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that class.



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Okay.



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So just like the constructor district it is also called once in the lifetime of an object.



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So a vendor destructively be called and destructively be when the scope of the object finish when scope



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of object finish then destructively be called and when the constructor is called when we create object



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Mr. constructor is called when we create object district it is called when this call of the object finish.



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Okay Destructor is also called once in a lifetime and concept is also called once in the lifetime of



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an object.



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So just like constructor we can create our own destructor but we do not pass any argument again we cannot



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pass any argument to the destructor.



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So constructors can be many they can be many constructor in a program in a class but destructive will



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only be one they will be only one district in a class.



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Okay.



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What happened is if we will create our own construct that then default constructor goes.



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If we will create our own constructor default constructor goes away.



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Similarly if we will create our destructor then and build construct it goes away and our destructively



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becalmed Okay so let's say in code



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special symbol district the name is same as the name of the class and that's all.



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Let's bring something here.



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So see out



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Mr. Picard



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Okay so now since we have written our own destructor so our destructively record.



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Okay



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our will be called inbuilt Destructor is not available to us any mode



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our destructor will be called because we created our own destructor.



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And then when destructor will not be called Okay so random destructive will be called when this call



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of the object finish so we can see here we have three objects two objects has start tick and one objects



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and dynamic so add this line.



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Line number 15 the scope of the object finish.



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So as soon as we reach line number 15 destructor will be called.



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Okay destructively be.



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As soon as with each line number 15.



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Okay.



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So what should be our output



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so at this line construct the number three call which is a pyramid based constructor again paramedics



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constructively called construct that recall again constructed recall.



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Now when we reach this line output will be destructor called



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again destructor called and again destructor called divide two times because we have three objects.



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So three objects so two time destructor will be called for allocating the memory of the object.



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Okay so this is our expected output.



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And now let us in this file so first we have to read this file because we need changes to this file



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and now we will run this file



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so construct that record construct let's recall.



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So this time constructor takes call for as one concept to take a while for us to construct that recall



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for history.



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Now Mr. Special Destructor is being getting called only two times Destructor is called only two times



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but we have three objects.



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So why Destructor is called two times why not two times.



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So let us try to understand why two times and why not three.



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So what is the effect of the slain agent Ben number is hundred and this is our student s one and let's



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say this is 500 what is the effect of this line age will be twenty.



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Rule number is two hundred and student two and let's say this is six hundred what is the effect of this



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line.



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So we are creating the object dynamically so we have a point that is three and then in the heap memory



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we have ages today and rule number is 200



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okay let's say it's Airbus's seven.



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Okay and then we are doing some stuff okay so at this line what will happen.



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Constructor should be called.



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So what constructively do it will destroy the memory it will they allocate the object.



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So only these parts will be deleted on distracting memory will be deleted only starting objects will



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be deleted.



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Okay so this is not a static object.



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So constructor will not be calling for this Saudi district will not be called for this district will



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only destroy this object and this object and since this is not object as trees art object destructive



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of history will not recall.



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Okay so our destructor will destroy only these two objects destructively be coiled for these two and



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not for S3 because this is simple appoint a variable it is not an object.



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So what we have to do it is our responsibility we have to delete this class we have to delete this object



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okay it is our responsibility to delete this object.



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Now how can we delete this object.



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So in the dynamic memory location we have studied how to delete dynamic memory using a keyword called



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delete.



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So we will write delete s.t. word delete activity do it will come here and as soon as we will come here



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destructor for this object will be called destructor for as tree will be called and this memory will



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get deleted this memory will get deleted.



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Okay so always remember always remember if there is a dynamic memory allocation then binding memory



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allocation has to be deleted by ourself.



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Okay.



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They are not automatically deleted only static memories static objects they are deleted automatically



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for dynamic memory to be allocate we have to use the keyword delete.



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Now let us destroy object as tree or delete tree now destructively recorded.



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Okay



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see District based being getting called three times okay.



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So this is all about destructor.



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Thank you.