1
00:00:05,140 --> 00:00:07,640
As we've stepped through our code in the debugger,

2
00:00:07,640 --> 00:00:11,240
you've seen an identifier named this in the debugger pane.

3
00:00:12,040 --> 00:00:16,190
This is a reserved keyword that contains the address of the current object.

4
00:00:16,550 --> 00:00:20,950
So it's a pointer to the object that's currently being used by the class member methods.

5
00:00:21,310 --> 00:00:24,640
The this keyword can only be used within the scope of the class.

6
00:00:25,240 --> 00:00:27,940
In many other object-oriented programming languages,

7
00:00:27,940 --> 00:00:30,300
we use the word self instead of this.

8
00:00:30,600 --> 00:00:32,960
But in c++,  we use the keyword this.

9
00:00:33,860 --> 00:00:36,860
All member access is done via the this pointer.

10
00:00:37,360 --> 00:00:40,760
However, c++ allows you to use member names directly.

11
00:00:40,760 --> 00:00:43,660
And behind the scenes, it's actually using this pointer.

12
00:00:44,020 --> 00:00:47,680
This can be used by the programmer, and in many cases, we must use it.

13
00:00:48,180 --> 00:00:51,480
We can use it to explicitly access data members and methods.

14
00:00:51,480 --> 00:00:54,680
We can also use it to determine if two objects are the same.

15
00:00:55,480 --> 00:00:58,480
We'll use this in the next section when we overload the assignment

16
00:00:58,480 --> 00:01:01,080
operator to determine if we're assigning to ourselves.

17
00:01:02,080 --> 00:01:06,280
Of course, since this points to the current object if you de-reference it,

18
00:01:06,280 --> 00:01:09,180
you'll follow the pointer and work with the current object.

19
00:01:11,380 --> 00:01:15,680
Here's an example of one way to write the set balance method for an account class.

20
00:01:15,680 --> 00:01:18,340
Notice that the name of the parameter is bal

21
00:01:18,340 --> 00:01:21,340
and the code in the body of the method is balance equals bal,

22
00:01:21,890 --> 00:01:26,040
which assigns the value of the parameter bal to the class data member balance.

23
00:01:26,400 --> 00:01:29,000
We don't have to write this arrow balance

24
00:01:29,000 --> 00:01:32,200
but that's exactly what the compiler is doing for us behind the scenes.

25
00:01:33,900 --> 00:01:36,890
Now suppose that the name of the parameter was balance.

26
00:01:36,890 --> 00:01:39,190
Now in the method body, the assignment statement

27
00:01:39,190 --> 00:01:42,550
balance equals balance would use the parameter balance for

28
00:01:42,550 --> 00:01:46,050
both of those identifiers instead of the data member balance.

29
00:01:46,050 --> 00:01:47,550
That's because of scope rules.

30
00:01:48,540 --> 00:01:51,530
Now this statement would not accomplish what we wanted to do.

31
00:01:51,530 --> 00:01:54,190
So in order to refer to the data member balance,

32
00:01:54,190 --> 00:01:57,550
we need to explicitly use this arrow balance.

33
00:01:58,910 --> 00:02:02,600
Finally, suppose we have a compare balance method in the account class

34
00:02:02,600 --> 00:02:05,100
that compares the balance of one object with another.

35
00:02:05,760 --> 00:02:10,020
We could check to see if we're comparing the same objects by comparing this

36
00:02:10,020 --> 00:02:11,620
and the address of other.

37
00:02:11,980 --> 00:02:14,780
If they're the same, then we're dealing with the same object.

38
00:02:15,330 --> 00:02:16,330
In this example,

39
00:02:16,330 --> 00:02:20,130
it wouldn't make much difference in our code since we're simply comparing balances.

40
00:02:20,130 --> 00:02:24,380
But if our compare logic is involved or computationally expensive,

41
00:02:24,380 --> 00:02:28,070
then a quick check to see if the objects are the same could help performance.

42
00:02:28,430 --> 00:02:32,530
We'll use the this pointer again in the operator overloading section of the course.