Table Of Contents
Case Structure (Clock-Driven Logic)
Contains one or more subdiagrams, or cases, exactly one of which executes when the structure executes.
The value wired to the selector terminal determines which case to execute.
Case Structures behave similarly to switch statements or if-then-else statements in other programming languages.
Programming Patterns
Selector
Value that determines which case to execute based on the input data. The input data can be a Boolean, string, integer, enumerated type, or error cluster. The data type you wire to the selector terminal determines what cases you can enter in the case selector label.
Case Selector Label
Tunnel
Point through which data enters the structure.
Matching Cases from the Items in a Control
The Case Structure matches cases using different values depending on the data type of the input you wire to the selector terminal.
| Selector Control | How LabVIEW Creates Cases |
|---|---|
| Ring | Cases match the numeric values of items in the control. |
| Enum | Cases match the string values of items in the control rather than the numeric values. |
Troubleshooting an Unexpected Execution of the Default Case
If the default case executes unexpectedly, verify that the input values wired to the selector terminal match the values in the case selector label exactly.
Requirements for Undefined Cases
An edit-time error occurs when there are values of the selector data type that do not correspond to any subdiagram in the Case Structure. You must either define a default case to handle out-of-range values or create a case for every possible input value. For example, if the selector is an integer data type and you specify cases for 1, 2, and 3, you must specify a default case to execute if the input value is 4 or any other unspecified integer value.
Entering Values in the Case Selector Label
You can enter a single value or lists and ranges of values in the case selector label of a Case Structure, as shown in the following table.| Type of Values | Description |
|---|---|
| Numeric ranges | Specify a range as 10..20, meaning all numbers from 10 to 20 inclusively. |
| Open-ended numeric ranges | Specify a range as ..100, meaning all numbers less than or equal to 100, or 100.., meaning all numbers greater than or equal to 100. |
| Lists and ranges | Use commas to separate values, for example ..5, 6, 7..10, 12, 13, 14. |
| Enumerated values | The values display in quotation marks, for example "red", "green", and "blue". However, you do not need to type the quotation marks when you enter the values unless the string or enumerated value contains a comma or range symbol ("," or ".."). A string value accepts the following backslash codes for non-alphanumeric characters: \r for a carriage return, \n for a line feed, \t for a tab, and \s for a space. |
Where This Node Can Run:
Desktop OS: none
FPGA: All devices
Web Server: Not supported in VIs that run in a web application