# Auto vs. Variant, when to use Auto? **URL:** \ **Category:** General\ **Created:** [May 11, 2015, 3:50am UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169 "2015-05-11T03:50:54Z")\ **Posts on this page:** 8\ **Page:** 5
**Author:** ![Rob\_Egal](https://forum.xojo.com/letter_avatar_proxy/v4/letter/r/76d3ee/32.png) [@Rob\_Egal](https://forum.xojo.com/u/Rob_Egal)\ **Post date:** [August 17, 2015, 8:33am UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/81 "2015-08-17T08:33:50Z")
The general concept of the auto data type is good and the right way. Using introspection to determine type information is no problem but in terms of performance it could be tweaked a bit. ---
**Author:** ![Eli\_Ott](https://forum.xojo.com/letter_avatar_proxy/v4/letter/e/5f8ce5/32.png) [@Eli\_Ott](https://forum.xojo.com/u/Eli_Ott)\ **Post date:** [August 17, 2015, 9:00am UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/82 "2015-08-17T09:00:44Z")
> [@207494:@Rob Egal](#): > > but in terms of performance it could be tweaked a bit. It would be great if that was built in. The Variant data type had a good and a bad side: The good was that you could query it for the data type it was holding in a fast way. The bad that you were able to assign the value to whatever data type you wanted (causing hard to find bugs due to having no compile time checks). Unfortunately Xojo now leaves the good part of Variant up to you too. I created a module called “Auto” with extension methods to exactly mimic the Variant Type method and the TypeInteger, TypeBoolean, etc. constants. But used in loops it shows to be a lot slower than Variant’s Type method. ---
**Author:** ![Rob\_Egal](https://forum.xojo.com/letter_avatar_proxy/v4/letter/r/76d3ee/32.png) [@Rob\_Egal](https://forum.xojo.com/u/Rob_Egal)\ **Post date:** [August 17, 2015, 11:25am UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/83 "2015-08-17T11:25:14Z")
[quote=207498:@Eli Ott]It would be great if that was built in. The Variant data type had a good and a bad side: The good was that you could query it for the data type it was holding in a fast way. The bad that you were able to assign the value to whatever data type you wanted (causing hard to find bugs due to having no compile time checks). Unfortunately Xojo now leaves the good part of Variant up to you too. I created a module called “Auto” with extension methods to exactly mimic the Variant Type method and the TypeInteger, TypeBoolean, etc. constants. But used in loops it shows to be a lot slower than Variant’s Type method.[/quote] To be honest I don’t see it built in but let’s see what the future brings… ---
**Author:** ![Joe\_Ranieri](https://forum.xojo.com/letter_avatar_proxy/v4/letter/j/43a26b/32.png) [@Joe\_Ranieri](https://forum.xojo.com/u/Joe_Ranieri)\ **Post date:** [August 17, 2015, 12:42pm UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/84 "2015-08-17T12:42:17Z")
> [@207513:@Rob Egal](#): > > To be honest I don’t see it built in but let’s see what the future brings… The eventual idea will be that you will be able to do something like: `Select Case Xojo.Introspection.GetType(myAuto) Case GetTypeInfo(Integer) // stuff Case GetTypeInfo(Text) // other stuff End Select` ---
**Author:** ![Eli\_Ott](https://forum.xojo.com/letter_avatar_proxy/v4/letter/e/5f8ce5/32.png) [@Eli\_Ott](https://forum.xojo.com/u/Eli_Ott)\ **Post date:** [August 17, 2015, 12:50pm UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/85 "2015-08-17T12:50:55Z")
It is slow (it involves string comparison). It is error-prone. Each developer has to re-invent the wheel. [code] Dim typeInfo As TypeInfo = GetType(value) If typeInfo Is Nil Then // Nil ElseIf typeInfo.IsPrimitive Then Select Case typeInfo.Name Case “Boolean” // Boolean Case “Color” // Color Case “Int8”, “Int16”, “Int32”, “UInt8”, “UInt16”, “UInt32” // Integer Case “Int64”, “UInt64” // Long Case “Single” // Single Case “Double” // Double Case “Currency” // Currency Case “Text” // Text Case “Ptr” // Ptr Case “CString” // CString Else … // TODO End ElseIf typeInfo.IsValueType Then // Structure // This is just a guess, as there is no TypeInfo.IsStructure property ElseIf typeInfo.IsClass Then If typeInfo.Name = “Xojo.Core.Date” Then // Date Else // Object, but not a Xojo.Core.Date End ElseIf typeInfo.IsArray Then Select Case typeInfo.ArrayElementType.Name Case “Boolean” // Array of Booleans Case “Color” // Array of Colors … and so on, you get the picture … End Else // more? End[/code] ---
**Author:** ![Brock\_Nash](https://forum.xojo.com/user_avatar/forum.xojo.com/brock_nash/32/1126_2.png) [@Brock\_Nash](https://forum.xojo.com/u/Brock_Nash)\ **Post date:** [August 17, 2015, 1:17pm UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/86 "2015-08-17T13:17:52Z")
[quote=207523:@Joe Ranieri]The eventual idea will be that you will be able to do something like: `Select Case Xojo.Introspection.GetType(myAuto) Case GetTypeInfo(Integer) // stuff Case GetTypeInfo(Text) // other stuff End Select`[/quote] Wouldn’t it be better if Xojo just did an Auto.Type method then? I mean we could always build an extension method but it seems silly to have the user have to use Xojo.Introspection.GetType for something so key to using Auto. `Select Case myAuto.Type Case GetTypeInfo(Integer)` ---
**Author:** ![Rob\_Egal](https://forum.xojo.com/letter_avatar_proxy/v4/letter/r/76d3ee/32.png) [@Rob\_Egal](https://forum.xojo.com/u/Rob_Egal)\ **Post date:** [August 17, 2015, 1:34pm UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/87 "2015-08-17T13:34:34Z")
[quote=207523:@Joe Ranieri]The eventual idea will be that you will be able to do something like: `Select Case Xojo.Introspection.GetType(myAuto) Case GetTypeInfo(Integer) // stuff Case GetTypeInfo(Text) // other stuff End Select`[/quote] That’s good so far. I didn’t mean it in any other way. ---
**Author:** ![system](https://forum.xojo.com/uploads/default/original/1X/455b4dcc0e61630e9f81940004ddffa49c432a46.png) [@system](https://forum.xojo.com/u/system)\ **Post date:** [October 29, 2020, 5:45pm UTC](https://forum.xojo.com/t/auto-vs-variant-when-to-use-auto/24169/88 "2020-10-29T17:45:01Z")
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