any downsides to that? This is generally frowned upon because of a lack of type info - you need reflection to figure out what's in each entry - but if you're coming from a dynamic language you're probably used to working without type safety anyway. New comments cannot be posted and votes cannot be cast. Let's look at options which approximate that. In some places I use it as is -- as an array of St1. Go doesn't do that directly. Just because you can do a thing doesn't mean you should do a thing. This post desicribes inheritance using struct only. Refer this link for more details –, By using interface + struct – This fixes the limitations of above two approach but one limitation is that overriding methods is not possible. There are different ways of doing it and each having some limitations. There are different ways of doing it and each having some limitations. Don't know yet if I like this or not, but hey, look at it and see if this is something usable for you. Option 3: This is the closest to a Javascript object: instead of a struct use a map[string]interface{}. OP: This sounds like an XY problem. It doesn't really map to how you solve problems in Go in a typical way. The different ways are: By using embedded struct – The parent struct is embedded in child struct. Go supports inheritance by embedding struct or using interface. Refer to this link for more details –. What would be the key in a map? is it possible to extend a type ? See below code: Subtyping is not supported. Go is a statically typed language so you'll have to "cast" your results each place you need the field. Structs aren't JavaScript objects or Python dicts. You can add a func GetField("fieldName") interface{} getter to your struct type. Option 2: Optional fields in a struct. Instead of asking about Y (forcing dynamic stuff into a static language) if you describe X (what you really need to do that you think requires dynamic stuff) you'll likely get a straight forward idiomatic Go way of accomplishing X that will work much better, be much cleaner, be easier to read, understand, debug, etc. Press question mark to learn the rest of the keyboard shortcuts. You cannot pass the child struct to a function that expects base. Cookies help us deliver our Services. I have a struct St1. Option 1: Have multiple structs, give them a common interface, and have an array of that interface. For example in the above code if you uncomment //check(child) it will give compilation error: “cannot use child (type *child) as type base in argument to check”. That's what you want to do based on your experience with other languages. Each data field in a struct is declared with a known type, which could be a built-in type or another user-defined type. Take a step back and maybe describe what problem you think this is the solution to, and maybe people can suggest a different approach. Let's look at options which approximate that. The easiest is to add a map[string] interface{} to your struct. If you're thinking from a dynamic language then there's no solution that's going to be particularly comfortable for you. a struct itself? Do visit our Inheritance in Go Complete Guide post for full reference. This package is an example of something you should not do in Go. The different ways are: In inheritance using a struct, a base struct is embedded in child struct and base properties and methods can directly be called on child struct. But there is a workaround. A struct (short for "structure") is a collection of data fields with declared data types. ... the library contains the structs and the data being passed by the user matches these structs, however I may need to add a few additional fields that the library doesnt need by my rest wrapper will use. If you don't know what extra fields are there ahead of time this won't work. By using our Services or clicking I agree, you agree to our use of cookies. Golang has the ability to declare and create own data types by combining one or more types, including both built-in and user-defined types. Option 2: Optional fields in a struct. Press J to jump to the feed. Option 1: Have multiple structs, give them a common interface, and have an array of that interface. Go supports inheritance by embedding struct or using interface. If those fields are the same type you could create a structure having those additional "fields" and put a pointer in struct St1 to such a struct. In other place I need to be able to dynamically attach extra data to each struct, akin to adding a few additional fields *dynamically* to each St1. Go doesn't do that directly. Structs aren't JavaScript objects or Python dicts. You can't avoid casting at the location where you'll use the field's value. I remembered I saw something last year and here it is: https://github.com/Ompluscator/dynamic-struct. Ask questions and post articles about the Go programming language and related tools, events etc. If you don't know what extra fields are there ahead of time this won't work. The limitation is … To fix this we can do inheritance using Interface, Variables in Go (Golang) – Complete Guide, OOP: Inheritance in GOLANG complete guide, Using Context Package in GO (Golang) – Complete Guide, Understanding time and date in Go (Golang) – Complete Guide, By using interfaces – Subtyping is possible but the limitation is that one has no way to refer to common properties.
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