View source for Diagram Disable structure

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{{LabVIEW Palette Object Information|palette=Functions Palette/Programming/Structures{{!}}Structures palette|type=structure|icon=Functions Palette - Programming - Structures - Diagram Disable Structure.png}}
[[File:Diagram Disable Structure - Components.png|thumb|Components of a Diagram Disable structure]]

A '''Diagram Disable Structure''' is a primitive [[Functions Palette/Programming/Structures|structure]] that can have one or more [[Subdiagram|subdiagrams]] (also known as "Cases"), one of which is executed at runtime. The programmer must manually specify the subdiagram to execute. Disabled subdiagrams do not break a VI if they contain broken wires or SubVIs.

== Usage ==
=== Code execution ===
[[File:Diagram Disable Structure - Case selector with two disabled cases.png|thumb|Diagram Disable structure with two disabled cases]]
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.

{| class="wikitable"
! Enabled
| The subdiagram will be executed at runtime.
|-
! Disabled
| The subdiagram will be ignored.
|}

Only the ''Enabled'' case will be executed, while all other cases will be ignored. The ''Enabled'' case is highlighted in the Case selector with the prefix <tt>[*]</tt>.

=== Changing the Enabled case ===
[[File:Diagram Disable Structure - Enable This Subdiagram.png|thumb|Enable the currently selected subdiagram]]
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.

{| class="wikitable"
! Enable This Subdiagram
| Enables the currently selected subdiagram (must be disabled) and disables all other subdiagrams.
|-
! Disable This Subdiagram
| Disables the currently selected subdiagram (must be enabled).
|}

=== Similarities with Case structures ===

{{ambox|type=style|text=The examples below have indicators ''inside'' structures, which is considered bad practice. They need to be replaced once file versioning works again. --[[User:Logmanoriginal|Logmanoriginal]] ([[User talk:Logmanoriginal|talk]]) 20:40, 6 August 2019 (UTC)}}

The Diagram Disable structure is similar to the [[Functions Palette/Programming/Structures/Case Structure|Case structure]]. Both can have multiple subdiagrams and only one will be executed at runtime. The key difference is, that Case structures are evaluated at runtime while Diagram Disable structures are evaluated at compile-time. Before the addition of Diagram Disable structures in [[LabVIEW 8|LabVIEW 8]], Case structures with a constant value wired to the Case Selector terminal were the only way to disable code.<ref>[https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P9NASA0 NI Knowledge Base: Comment Out or Disable Pieces of Code in LabVIEW]</ref> In that regard, Case structures work the same as Diagram Disable structures.

[[File:Diagram Disable Structure - Example with Case structure.png|thumb|left|Unreachable code in a Case structure with constant value wired to the Case Selector terminal]]

A Diagram Disable structure, however, conveys the '''intention''' of the programmer and does not break the VI if a disabled case contains broken code.

{|
| [[File:Diagram Disable Structure - Compare to Case structure 1.png|thumb|center|Broken disabled code in a Diagram Disable structure does not break the VI]]
| [[File:Diagram Disable Structure - Compare to Case structure 2.png|thumb|center|Broken disabled code in a Case structure with constant value wired to the Case Selector terminal breaks the VI]]
|}

== 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|debugging]] VIs.
* Use a [[Version Control Systems|version control system]] instead of Diagram Disable structures to manage code revisions.
* Use [[Functions Palette/Programming/Structures/Conditional Disable Structure|Conditional Disable structures]] instead of Diagram Disable structures to enable/disable subdiagrams based on compile-time conditions.

== History ==

{| class="wikitable"
! Version
! Change(s)
|-
| [[File:LV2019.png|frameless|border|64x64px|LabVIEW 2019|link=LabVIEW 2019]]
| The Diagram Disable structure can automatically be replaced by a [[Functions Palette/Programming/Structures/Type Specialization Structure|Type Specialization Structure]]
|-
| [[File:LV8-2013.png|frameless|border|64x64px|LabVIEW 8|link=LabVIEW 8]]
| The ''Diagram Disable'' structure was added.
|}

== See Also ==
* [[DisableStructure class]]
* [[Functions Palette/Programming/Structures/Conditional Disable Structure|Conditional Disable Structure]]
* [[Functions Palette/Programming/Structures/Type Specialization Structure|Type Specialization Structure]]

== References ==
<references />

[[Category:Diagram Disable Structure]]
[[Category:Structures Palette]]
[[Category:Debugging]]