Correct struct definition

Question

How to define the struct in the correct way, look at the following code snippet:

defmodule SapOdataService.Worker do defstruct uri: "", user: nil, password: nil

Should I define the default value as nil or?

Depends on your usecase, you can define custom default values or just pass a list of atoms to the defstruct and every value will have a nil as a default, which may make sense in your case I guess. — NoDisplayName
– NoDisplayName, Commented Dec 19, 2016 at 12:44
Well, sometimes, for let's say url value it makes sense to leave nil as a default value, sometimes it makes sense to make "example.com" as a default value, sometimes it makes sense to make it an empty string and etc. It's completely up to you and what you think it more suitable for your situation. — NoDisplayName
– NoDisplayName, Commented Dec 19, 2016 at 13:53
You can also combine both and write something like defstruct [:user, :password, url: ""], so you don't have to repeat nil over and over. — Patrick Oscity
– Patrick Oscity, Commented Dec 19, 2016 at 14:37

fny · Accepted Answer · 2016-12-20 21:35:20Z

You have a few options.

You can list the key value pairs explicitly using nil for blank values
```
defmodule User do defstruct name: "zero_coding", age: nil end 
```
You can pass a list of atoms that will all default to nil:
```
defmodule User do defstruct [:name, :age] end 
```
You can do a mix of the above a list of atoms that will all default to nil:
```
defmodule User do defstruct [:age, name: "zero_coding"] end 
```
You can also enforce specific keys that must be specified when creating the struct
```
defmodule User do @enforce_keys [:name] defstruct [:name, :age] end 
```

here type 3 only works if you put first all the default-less (implicit nil) first, then the explicit defaults. defstruct [name: "zero_coding", :age] gives error.

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