Golang equivalent of pythons getattr() or call() [duplicate]

Question

I would like to manipulate structs at Runtime.

For example, I have a struct:

type Item struct {
 SomeField string
}

Is it possible to add field on runtime? Or Access Attribute that is not yet defined. Something like pythons __getattr__() or __call__() so I could dynamically control the fields/methods accessed.

E.g. do something like Item.DynamicField or Item.DynamicMethod() where I don't know exactly the Field or the Method that will be accessed/called, So I can't define it statically.

Maybe I'm missing something in the Reflect package?

Thank you.

@OneOfOne The getattr and call methods have nothing to do with static typing. The first is related to introspection, and the second is a way of treating an object as a function so it can be "called" as though it was a function. The builtin reflect package can be used to get exported attributes. I don't know of an equivalent to the call method in Go, but I don't think you it is essential: just create an anonymous function that includes a ref to the object and pass that function instead of the object. — Oliver
– Oliver, Commented Dec 13, 2022 at 1:47

warvariuc · Accepted Answer · 2014-07-05 12:39:07Z

8

https://github.com/oleiade/reflections

The purpose of reflections package is to make developers life easier when it comes to introspect structures at runtime. Its API is inspired from python language (getattr, setattr, hasattr...) and provides a simplified access to structure fields and tags.

answered Jul 5, 2014 at 12:39

warvariuc

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Denys Séguret · Accepted Answer · 2014-06-19 15:42:34Z

8

Is it possible to add field on runtime? Or Access Attribute that is not yet defined.

No. Go is a compiled language with statically defined types. You probably need a map if you want to dynamically add properties.

answered Jun 19, 2014 at 15:42

Denys Séguret

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4 Comments

Bndr Over a year ago

Ok, and at compile time?

Denys Séguret Over a year ago

What does that mean ? You can preprocess your code to augment it of course, and Go contains static analysis and transformation tools, but it's clear that you're facing a xy problem.

Not_a_Golfer Over a year ago

If OP just wants to wrap access to members (for example for logging or access control), it can be done with reflection. Though I highly suggest against it.

twotwotwo Over a year ago

Go isn't the sort of language you're expecting--your main dynamic tools are interfaces and embedding here. The sort of question we can answer is more like "I want to build an app that does XYZ and can't think of any way to do it in Go." (e.g., stackoverflow.com/questions/19759274/…) And we'll give it a shot, though it might not be concise as it would be in Python.

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