Creating types from json samples

1

Hi,
I’m trying to avoid writing boilerplate code that transforms json data into typed values. Did my homework and researched thoroughly, but couldn’t spot a library that helps with that. Found one for typescript though, that does just what I need - you give it some json samples, and it generates all the types needed.

Question is: do we have some library I couldn’t find? If not, how would you go about creating one?

Thanks in advance!

2

I think you can generate ts types from the tool you mention and then use ts2hx.

3

There are macros for that.

I’m not sure if I’m allowed to distribute the one I am using, but it’s not much (~150 loc for the whole thing). It takes a json at compile time and make the data (nested data too) available via static inline vars and internal types (so completion works). It’s only meant for static data, though.

4

It doesn’t even have to be a macro. One could write a simple script that parses the json using haxe.Json.parse, determines value types (using Type.typeof and/or Std.is) from that, constructs an anonymous structure definition as haxe.macro.Expr.TypeDefinition and then prints it out using new haxe.macro.Printer().printTypeDefinition. Sounds like a nice exercise for a Haxe enthusiast :slight_smile:

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5

Andy shared a nice trick using $type() in this thread, and made an example in try haxe.

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6

There it is Haxe Json def :slight_smile:

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7

yes I did that :stuck_out_tongue: GitHub - MatthijsKamstra/hxjsondef: HxJsonDef is command-line app written in Haxe that helps you quickly define a typedef from some arbitrary .json

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