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November 10, 2018 How do I use null in a struct? | ||||
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I'm making a Rest API with vibe.d and I have a struct User. Sometimes I need to return only a few of the fields. So for example: return User(1, null, "John", null, null, ...); If I do this, an error occurs: cannot implicitly convert expression null of type typeof(null) to ... Thanks. |
November 10, 2018 Re: How do I use null in a struct? | ||||
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Posted in reply to Václav Kozák | On 10.11.2018 22:42, Václav Kozák wrote: > I'm making a Rest API with vibe.d and I have a struct User. Sometimes I need to return only a few of the fields. So for example: return User(1, null, "John", null, null, ...); > If I do this, an error occurs: cannot implicitly convert expression null of type typeof(null) to ... > Thanks. Probably you need Nullable? https://dlang.org/phobos/std_typecons.html#Nullable |
November 10, 2018 Re: How do I use null in a struct? | ||||
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Posted in reply to Václav Kozák | On Saturday, 10 November 2018 at 19:42:47 UTC, Václav Kozák wrote: > I'm making a Rest API with vibe.d and I have a struct User. Sometimes I need to return only a few of the fields. So for example: return User(1, null, "John", null, null, ...); > If I do this, an error occurs: cannot implicitly convert expression null of type typeof(null) to ... > Thanks. You can use Optional like drug said, or you can use the @optional attribute [1]. @optional will leave the field in its .init state, whereas with Optional its easier to detect the null state. [1] http://vibed.org/api/vibe.data.serialization/optional |
November 12, 2018 Re: How do I use null in a struct? | ||||
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Posted in reply to Václav Kozák | On Saturday, 10 November 2018 at 19:42:47 UTC, Václav Kozák wrote: > I'm making a Rest API with vibe.d and I have a struct User. Sometimes I need to return only a few of the fields. So for example: return User(1, null, "John", null, null, ...); > If I do this, an error occurs: cannot implicitly convert expression null of type typeof(null) to ... > Thanks. Another choice: https://github.com/huntlabs/hunt/blob/master/source/hunt/lang/Nullable.d This Nullable is a class and we are using it. |
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