Diagram Disable structure
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A Diagram Disable Structure is a primitive structure that can have one or more subdiagrams (also known as "Cases"), one of which is executed at runtime. The programmer must manually specify the subdiagram to execute during runtime. Disabled subdiagrams do not break a VI if they contain broken wires or SubVIs.
Code execution
The Diagram Disable structure can have one or more cases, each of which can be Enabled or Disabled. However, only one subdiagram can be Enabled at any time.
| Enabled | The subdiagram will be executed at runtime. |
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| Disabled | The subdiagram will be ignored. |
Only the Enabled case is executed, while all other cases are ignored during execution. The Enabled case is highlighted in the Case selector with the prefix [*].
Changing the Enabled case
The Enabled case can be changed via the right-click menu option Enable This Subdiagram for disabled cases or Disable This Subdiagram for the enabled case.
| Enable This Subdiagram | Enables the currently selected subdiagram (must be disabled) and disables all other subdiagrams. |
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| Disable This Subdiagram | Disables the currently selected subdiagram (must be enabled). |
Similarities with Case structures
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The examples below have indicators inside structures, which is considered bad practice. They need to be replaced once file versioning works again. --Logmanoriginal (talk) 20:40, 6 August 2019 (UTC) |
The Diagram Disable structure is similar to the Case structure, which can also have multiple subdiagrams, one of which is executed at runtime. In fact, before the invention of Diagram Disable structures in LabVIEW 8, Case structures were the only way to disable code by wiring a constant value to the Case Selector terminal.[1] In that regard, Case structures work the same as Diagram Disable structures.
A Diagram Disable structure, however, conveys the intention of the programmer and does not break a VI if the code inside a disabled case breaks.
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Best practice
- Use Diagram Disable structures instead of Case structures to disable sections of code.
- Use Diagram Disable structures to temporarily disable sections of code when debugging VIs.
- Use a version control system instead of Diagram Disable structures to manage code revisions.
- Use Conditional Disable structures instead of Diagram Disable structures to enable/disable subdiagrams based on compile-time conditions.
History
| Version | Change(s) |
|---|---|
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The Diagram Disable structure can automatically be replaced by a Type Specialization Structure |
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The Diagram Disable structure was added. |