CODEWITHSUNDEEP
c++design-patterns
Aminos
Aminos

Reputation: 871

identifying the design pattern name used

I want to check if the examples below (from a test interview) corresponds to the correct design pattern name :

Example 1 : can that piece of code illustrate the "Builder" pattern or it might be the "Strategy" one ?

FileStream* files = new FileStream("my_file.zip");
BufferedStream* bufferds = new BufferedStream(files);
ZipStream* zips = new ZipStream(bufferds);

Example 2 : is the code below represent the "Strategy" pattern ?

struct UnixText {
void write(string str) { cout << str; }
void lf() { cout << "\n"; }
};

struct WindowsText {
void write(string str) { cout << str; }
void crlf() { cout << "\r\n"; }
};

struct Writer {
virtual void write(string str) = 0;
virtual void newline() = 0;
virtual ~Writer() {}
};

struct UnixWriter : Writer {
UnixWriter(UnixText* tx) { _target = tx; }
virtual void write(string str) { _target->write(str); }
virtual void newline() { _target->lf(); }

private:
UnixText* _target;
};

struct WindowsWriter : Writer {
WindowsWriter(WindowsText* tx) { _target = tx; }
virtual void write(string str) { _target->write(str); }
virtual void newline() { _target->crlf(); }

private:
WindowsText* _target;
};

int main()
{
Writer* writer = (g_IsUnix) ? (Writer*) new UnixWriter(new UnixText()) : (Writer*) new WindowsWriter(new WindowsText());

writer->write("Hello");
writer->newline();
writer->write("World");

}

Upvotes: 1

Views: 770

Answers (1)

Ravindra Ranwala
Ravindra Ranwala

Reputation: 21124

The first example uses I/O streams and it is a good use of Decorator pattern. Here it has a constructor that takes an instance of the same abstract class or interface. That's the recognition key of the Decorator pattern

The second one, you are passing some Writing Strategy to the UnixWriter and WindowsWriter which is the context. So it can be considered as Strategy pattern. But you can still improve it by having a contract for Writing Strategy. So your concrete writers should only know about that super type rather than having references to concrete implementations. That will make your system more flexible.

Upvotes: 1

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