Serde_json null in Json file - how to parse in a struct

1

Hi,

I have a JSON file something like this.

{

	"name" : "S.Gopinath",
        "city: : "Chennai",
        "cell": "9x380x414x30",
        "own_aircraft" : null
}

I want to use serde_json to deserialize in to a struct.

My struct could be as following.

struct myself {

	name : String,
        city : String,
        cell : String,
        own_aircraft : ???
	//Should I use enum Option ?
}

ow to accept the values for "null" which is supported as a type in JSON ?

Should I use Option type in the struct definition ?

2

Yes, use Option

1 Like
3

Option<YourAircraftType> is usually the way to go.

If you want to avoid Option, then the alternative is to add #[serde(default)] annotation to replace missing fields with their default values.

https://serde.rs/attr-default.html

This is handy if a field is Vec and you'd rather get an empty vec than deal with Option<Vec>.

2 Likes
4

Okay.. it works as I use Option.

struct myself {

	name : String,
        city : String,
        cell : String,
        own_aircraft : Option<String>,
}

Does it mean that when serde_json encounters null , it sets None for
own_aircraft and Some if it counters String ?

Right ?

Thanks,
S.Gopinath

5

Yes.

6

I don't think default works (without keeping Option) if there is an explicit null entry in the JSON.

7

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