Question

firstly, pardon my pseudo-code, i think in this case it is more legible than full code. Please assume that a property in the pseudo-code is in fact a field with a getter & setter method, except for the ArticleElement where it just needs be a property accessible from the object either by a direct getter method, or a two step getter method (ie getArticleSource().getName()).

Say i have a template entity:

ArticleTemplate
    Long id;
    String name;
    String description;
    Integer amount;
    Schedule schedule;

and it is used (via its schedule) to create many potential children entities on different dates:

Article
    Long id;
    String name;
    String description;
    Integer amount;
    Date date;
    Boolean complete;
    ArticleTemplate template;

some children entities are not created from a parent, they can be stand-alone (template can be null).

for my UI I want to create a sorted & merged list of :
a) potential children entities from parent entities
b) real children entities previously created from parent entities
c) orphan children entities created stand-alone

however, I need to add some properties to the elements of this list to determine the differences between the elements:

ArticleElement
    // actual value if from Article, null if from potential from ArticleTemplate
    Long id;
    // actual value if from Article or ArticleTemplate
    String name;
    // actual value if from Article or ArticleTemplate
    String description;
    // actual value if from Article or ArticleTemplate
    Integer amount;
    // actual value if from Article, simulated if from potential from ArticleTemplate
    Date date;
    // actual value if from Article, false if from potential from ArticleTemplate
    Boolean complete;
    // actual value (nullable) if from Article, self if from potential from ArticleTemplate
    ArticleTemplate template;
    // false if from Article, true if from potential from ArticleTemplate
    Boolean templateSimulation;
    // once the list is sorted, a running tally of this.amount is to be stored on this object
    Integer runningTally;
    // would be type of interface if Article and ArticleTemplate implement same
    Object source;

Clearly I’m going to have at least 3 classes but there’s a few different approaches with interfaces etc.

I’d like to avoid cloning and property copying wherever possible, and use inheritence wherever beneficial.

suggestions appreciated!

p.

Answer 1

Here’s my current solution, and i’m not sure I like it, but i haven’t come up with anything better just yet:

firstly, i’ll leave Article and ArticleTemplate alone. I could make them implement an interface describing their similarities but it doesn’t add much benefit for this case.

create the UI contract

public interface UiElement<T>
{
    T getSource();
    Class<T> getType();
    // redundant - refer to source
    // Long getId();
    String getName();
    String getDescription();
    Integer getAmount();
    Date getDate();
    Boolean getComplete();
    // redundant - not needed anymore
    // ArticleTemplate getTemplate();
    // redundant - replaced by getType()
    // Boolean getTemplateSimulation(); 
    Integer getRunningTally();
}

create implementation for Article – pass through contracted calls to the source object for most properties

public class ArticleUiElement implements UiElement<Article>
{
    private Article source;
    private Integer tally;

    public ArticleUiElement(Article source) {
        this.source = source;
    }

    public Article getSource() {
        return source;
    }

    public Class<Article> getType() {
        return Article.class;
    }

    public String getName() {
        return source.getName();
    }

    public String getDescription() {
        return source.getDescription();
    }

    public Integer getAmount() {
        return source.getAmount();
    }

    public Date getDate() {
        return source.getDate();
    }

    public Boolean getComplete() {
        return source.getComplete();
    }

    public String getRunningTally() {
        return tally;
    }

    public void setRunningTally(String tally) {
        this.tally = tally;
    }
}

create implementation for ArticleTemplate – pass through contracted calls to the source object for most properties

public class ArticleTemplateUiElement implements UiElement<ArticleTemplate>
{
    private ArticleTemplate source;
    private Integer tally;
    private Date date;

    public ArticleTemplateUiElement(ArticleTemplate source) {
        this.source = source;
    }

    public ArticleTemplate getSource() {
        return source;
    }

    public Class<ArticleTemplate> getType() {
        return ArticleTemplate.class;
    }

    public String getName() {
        return source.getName();
    }

    public String getDescription() {
        return source.getDescription();
    }

    public Integer getAmount() {
        return source.getAmount();
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public Boolean getComplete() {
        return false;
    }

    public String getRunningTally() {
        return tally;
    }

    public void setRunningTally(String tally) {
        this.tally = tally;
    }
}

can someone offer improvements, or an entirely better solution?