README.md

Todays refactoring comes from Martin Fowlers catalog of patterns. You can find this refactoring in his catalog here.

Yesterday we looked at extracting a subclass for moving responsibilities down if they are not needed across the board. A Collapse Hierarchy refactoring would be applied when you realize you no longer need a subclass. When this happens it doesn’t really make sense to keep your subclass around if it’s properties can be merged into the base class and used strictly from there.

public class Website {
	private String title;
	private String description;
	//This should NOT be a list of "Objects" but that's not the main point.
	private List<Object> pages;
	
	public String getTitle() {
		return title;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public List<Object> getPages() {
		return pages;
	}
	public void setPages(List<Object> pages) {
		this.pages = pages;
	}
}
public class StudentWebsite extends Website{
	private boolean isActive;

	public boolean isActive() {
		return isActive;
	}

	public void setActive(boolean isActive) {
		this.isActive = isActive;
	}
}

Here we have a subclass that isn’t doing too much. It just has one property to denote if the site is active or not. At this point maybe we realize that determining if a site is active is something we can use across the board so we can collapse the hierarchy back into only a Website and eliminate the StudentWebsite type.

public class Website {
	private String title;
	private String description;
	// This should NOT be a list of "Objects" but that's not the main point.
	private List<Object> pages;
	private boolean isActive;

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public List<Object> getPages() {
		return pages;
	}

	public void setPages(List<Object> pages) {
		this.pages = pages;
	}

	public boolean isActive() {
		return isActive;
	}

	public void setActive(boolean isActive) {
		this.isActive = isActive;
	}
}

Original C# code from the book:

public class Website {
	public string Title { get; set; }
	public string Description { get; set; }
	public IEnumerable<Webpage> Pages { get; set; }
}
public class StudentWebsite : Website{
	public bool IsActive { get; set; }
}

//Solution: 
public class Website {
	public string Title { get; set; }
	public string Description { get; set; }
	public IEnumerable<Webpage> Pages { get; set; }
	public bool IsActive { get; set; }
}