How to draw an Object Diagram in UML
Object diagrams are specific instances of class diagrams and are especially useful at presenting a high-level overview of your system. This tutorial will walk you through the steps of building an object diagram in Lucidchart.
Lucidchart is flexible enough for you to customize your object diagram to make it usable and beautiful. With an extensive array of UML shapes and connectors, you can create, edit and share—all from the canvas.Demo here Sign up free
How to Create an Object Diagram
Before you create an object diagram, take some time to review diagramming basics. Take a look at this UML diagram tutorial to gain a deeper understanding of the conventions of the Unified Modeling Language. Lucidchart's guide to Object diagrams explains that object diagrams are a type of class diagram, and when you might use one.
INCLUDE BASIC SYMBOLS
Object diagrams are one of the simplest kinds of UML diagrams. Visually, they resemble a pared-down class diagram. Objects are represented by simple rectangle shapes. You can include subdivisions in the rectangle to separate the title from its attributes. These shapes are then connected by lines that show the relationship between objects.
To create a UML object diagram, log in to Lucidchart. Select Create New Document > Blank UML. The UML shape libraries will populate the left side of your canvas. For a basic rectangle, drag out the Simple Class shape from the UML Class Diagram section. You can use the Icon Finder to add visual flair to your object diagram. This chart will map out three kinds of bank accounts, so search for “bank” and drag desired symbols onto your canvas.
One of the advantages of using Lucidchart for building object diagrams is that you have a high degree of control over line styles. For this diagram, we’ll use a solid diamond for the origin of the line, a solid black line, and an arrow on the end of the line. This will help the viewer see how all three accounts depend on the bank.
Make a line by dragging from a small circle on your first object. A dialog will appear: choose a rounded rectangle for the next shape. To add text in a shape in Lucidchart, simply double-click inside it.
ADD COLOR, TITLES, AND ATTRIBUTES
Object diagrams are designed to give a bird’s-eye view of a software system. This means that they lack some of the complex shape types found in other UML diagrams. Still, it is good to follow some basic conventions.
Think about the overarching category of each object (rectangle) in your diagram. For a car-centric diagram, this might be “Model;” for a family tree, this could be a member of a family, like “Father.” In this banking object diagram, we’re specifying accounts. We’ll use “Account 1: Savings” as the class title for this object.
Attributes do not need to be obscure. In this object, we’ve added the major identifiers of this particular savings account (balance, identity, interest rate, and minimum balance) as a list of class attributes after the title. Simply press Enter to start a new line. It’s easy to see how the particular attributes would change both for a different object (like a checking account, which would have a different interest rate) or the same object in a different scenario (savings account A will have a different ID with the bank than savings account B).
Lucidchart lets style your flowchart with customizable colors, fonts, and image import. Let’s keep this diagram simple. Make the class title bold by selecting it and using Ctrl or Cmd + B. When you’ve selected the shape, you can change the fill background from the top toolbar. Varying the object color makes it easy to distinguish accounts at a glance!
REVIEW YOUR WORK
Good job—you’ve created a workable object diagram in just a few steps! It’s always a good idea to get input from a colleague, supervisor, or friend on your UML diagrams. This version of your diagram is a first draft: check for typos, confusing relationships, and quality during the revision phase. Once you feel satisfied with the final product, download your chart as an image or PDF, or publish it to the web.
Lucidchart can help you create high-quality UML diagrams for your academic, business, or personal life. With an extensive shape library and wide variety of tutorials and examples, it’s easy to get started.