Combining the While Loop and Case Structure in LabVIEW

Main Loop

　　Almost all LabVIEW programs have at least one main loop that will continue to loop until the program ends. The program may end because of a stop button, an error, or other reasons. The following figure shows an example of a While Loop with a standard wait function (to prevent the program from monopolizing the CPU) and a stop button. 

　　This combination of While loop + Case structure is the basis for creating LabVIEW applications.

Handling Multiple Events in a While Loop

　　Let's start further discussion. What if there are multiple buttons? The simplest way is to add multiple Case structures in the While loop as shown below. This method is easy at the beginning, but it will be troublesome once you have more Case structures .

  

　　Now we know how to handle multiple events by combining While loop + Case structure. Similarly, if we want to handle N events, we can add N Case structures in the While loop. But what if there is not enough space in the flowchart? In this case, the solution of "adding another Case structure" is not so suitable. The solution to this situation is actually very simple, which is to create a Case structure with multiple cases, each case in this structure corresponds to an event.

　　In order to realize this idea, we need to create an array of Boolean variables, save the value of each button in this array and search the serial number of the element with the value TRUE in the array. Through this serial number, we can know which button is pressed and enter the number of the button into the case selection endpoint of the Case structure, and then the relevant operation corresponding to the button will be executed. As shown in the following figure: 

　　Now if you want to add a new event, you just need to add a new element to the array and add a corresponding case in the Case structure.

　　However, in actual use, we usually use enumerated type (enum) data to connect the case selection endpoints of the Case structure instead of straight I32 type integer data.