template <class Object> class MyVector : public vector<Object> in Java

Painting Code 39 Full ASCII in Java template <class Object> class MyVector : public vector<Object>
template <class Object> class MyVector : public vector<Object>
Code 3 Of 9 Printer In Java
Using Barcode creation for Java Control to generate, create Code39 image in Java applications.
public: explicit Myvector( int size = 0 : vector<Object>( size ) { }
Painting Bar Code In Java
Using Barcode printer for Java Control to generate, create barcode image in Java applications.
Iterator<Object> *getIterator( ) const { return new VectorIterator<Object>( this
Scan Barcode In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
An inheritance-based iterator design, in which getIterator returns a pointer to an iterator
Code 3 Of 9 Maker In Visual C#
Using Barcode encoder for .NET Control to generate, create USS Code 39 image in .NET applications.
The inheritancebased scheme introduces pointers (or references)The iterators are now allocated by new
Generate Code 39 In Visual Studio .NET
Using Barcode creator for ASP.NET Control to generate, create Code 39 image in ASP.NET applications.
Figure 517 shows the new MyVector,which returns a pointer to an Iterator object that is dynamically constructed by calling newBecause Vector1 terator IS-A Iterator,we can safely do so Note that the use of inheritance and polymorphism require that we introduce pointers or references Doing so muddies the code a bit, which is one reason why the STL is template based, rather than inheritance based Because getIterator creates and returns a new Iterator object, whose actual type is unknown, it is commonly called a factory method In general, a factory method creates a new concrete instance but returns it by using a pointer (or reference) to the abstract class The iterator classes are shown in Figure 518 First, we have the abstract class Iterator,which serves simply to establish the protocol by which all subclasses of Iterator can be accessed The protocol is specified with pure virtual functions As usual, we have a virtual destructor In order to keep the code short, we use the simplest protocol-that seen in design I (Section 541) This version of ~ e t orIt erat or is essentially identical to the original c implementation shown in Figure 515, except that it is a derived class of
Code-39 Creator In Visual Studio .NET
Using Barcode printer for .NET framework Control to generate, create Code 39 image in .NET applications.
Iterator
Creating Code 3 Of 9 In Visual Basic .NET
Using Barcode maker for VS .NET Control to generate, create Code39 image in .NET applications.
A factory method creates a new concrete instance but returns it by using a pointer (or reference) to the abstract class
Printing Bar Code In Java
Using Barcode maker for Java Control to generate, create bar code image in Java applications.
lterators
Paint USS Code 39 In Java
Using Barcode generator for Java Control to generate, create Code 39 Extended image in Java applications.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
Bar Code Creation In Java
Using Barcode creator for Java Control to generate, create bar code image in Java applications.
/ i A passive iterator class protocol / i Steps through its container
Print Bar Code In Java
Using Barcode creator for Java Control to generate, create barcode image in Java applications.
template <class Object> class Iterator
EAN-13 Generation In Java
Using Barcode maker for Java Control to generate, create GS1 - 13 image in Java applications.
public: virtual -Iterator(
Code 93 Full ASCII Encoder In Java
Using Barcode generation for Java Control to generate, create Code 93 Full ASCII image in Java applications.
virtual boo1 hasNext( ) const = 0 ; virtual const Object & next( ) = 0;
Code 39 Full ASCII Drawer In C#.NET
Using Barcode generation for Visual Studio .NET Control to generate, create Code-39 image in .NET framework applications.
/ / A concrete implementation of the iterator / / Could have been nested inside of Myvector!
Code 128A Creation In Visual Studio .NET
Using Barcode creator for ASP.NET Control to generate, create USS Code 128 image in ASP.NET applications.
template <class Object> class VectorIterator : public IteratoriObject> I public: VectorIterator( const MyVector<Object> *v ) : owner ( v ) , count ( 0 ) { } boo1 hasNext( ) const { return count ! = owner->size( const Object & next( ) { return (*owner)[ count++ 1 ; private: const MyVectoriObject> "owner; int count;
European Article Number 13 Recognizer In .NET
Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in .NET framework applications.
The iterator abstract class and a concrete implementation
Make EAN-13 In .NET Framework
Using Barcode printer for ASP.NET Control to generate, create EAN-13 Supplement 5 image in ASP.NET applications.
Figure 519 demonstrates how the inheritance-based iterators are used At line 10, the declaration of i tr : is now a pointer to an I teratorNowhere in main is there any mention of the actual VectorIterator type In fact, we could have written vector1 terator as a nested class in the private section or of ~ y ~te cThe fact that a vec tor1terator exists does not affect any clients of the MyVector class This is a neat design and illustrates nicely the idea of hiding an implementation and programming to an interface The changes to main are relatively minimal Lines 1 1 and 12 change because we must use operator-> instead of the dot operator
Creating Barcode In Visual Basic .NET
Using Barcode creation for VS .NET Control to generate, create bar code image in .NET applications.
Nowhere in main is there any of the actual iterator type
UPC A Creation In Visual Studio .NET
Using Barcode printer for ASP.NET Control to generate, create UPC Code image in ASP.NET applications.
Design Patterns
Paint ECC200 In Visual Studio .NET
Using Barcode printer for ASP.NET Control to generate, create Data Matrix image in ASP.NET applications.
1 int main( ) 2 { 3 MyVector<int> v; 4 5 vpush-back( 3 ) ; 6 vpush-back( 2 ) ; 7 8 cout < < "Vector contents: " << endl; 9 10 Iterator<int> *itr = vgetIterator( ) 11 while( itr->hasNext( ) ) 12 cout << itr->next( ) < < endl; 13 delete itr; 14 15 return 0 ; 16 17 1
An illustration of the use of iterators in inheritance-based design
The dynamically allocated iterator must be reclaimed by calling delete
Line 14 illustrates a disadvantage: The dynamically allocated iterator must be reclaimed by calling d e l e t e Remembering to do so all the time is annoying However, if we examine this situation closely, we can see a classic application of scenario #2 for the a u t o - p t r Recall from Section 531 (page 165) that in this scenario an object is allocated inside a function (in ) this case, g e t ~ t e r a t o rand is returned to the caller The caller is responsible for handling d e l e t e , which is exactly the situation in Figure 519 Thus although inconvenient, there is some support in the language to make our life easier By the way, recall that at the end of Section 531 (beginning on page 168), we explained that our version of ~ uo ~ o i n t e differed from the STL t r a u t o - p t r because that version allows any compatible pointers to be wrapped, whereas our version requires an exact type match We also explained that member templates could be used to loosen the requirement of an exact type match Looking at how a u t o - p t r would be used here, we see that we would need to do the following
1 In Figure 519, line 10, i t r would be an a u t o - p t r , and line 14 would disappear 2 In Figure 517, g e t I t e r a t o r would be rewritten to return an a u t o - p t r (line 18), and the result of new would be wrapped inside an a u t o - p t r (line 19)