How to represent an if condition1 else if contion2 on a sequence diagram?

问题

I was wondering, how can one represent "if cond1 else if cond2" statement on a sequence diagram?

    if (condition1) {
      // Do something
    } else if(condition2)
    {
      // Do something else if
    }

Im not sure if is it with two independent "Opt" clause

If possible create an image representation of a solution.

回答1:

In the sequence diagram, you can use a combined fragment with an alt operator. This allows you to show alternative behaviors:

• Graphically, the alternatives are in tiled regions separated by dashed horizotal lines.
• You can document the precise condition for each alternative in a guard (i.e. [condition]).

Example:

Additional reading:

• UML Basics: the sequence diagram (Article from Rational/IBM)

来源：https://stackoverflow.com/questions/38164421/how-to-represent-an-if-condition1-else-if-contion2-on-a-sequence-diagram