cannot borrow variables in object!

[ardawan]

I'm trying to create my data object and serialize it for sending through my network. but I'm not able to borrow "src" in my object.
I need the src to use it in the send_to() method.

is that a bug or the structure should be this way only?

let mut data = object!{
    "HEADER" => "RES:REGISTER",
    "SOURCE" => &src,
    "BODY" => object!{
        "UUID" => reg_serial
    }
};

// even i've tried this
//data["SOURCE"] = &src.into(); 

let serialised_data = json::stringify(data);
socket.send_to(&serialised_data.into_bytes(), &src).expect("cannot send");

the error is

error[E0277]: the trait bound `json::value::JsonValue: std::convert::From<&std::string::String>` is not satisfied
   --> src/main.rs:95:20
    |
95  |       let mut data = object!{
    |  ____________________^
96  | |         "HEADER" => "RES:REGISTER",
97  | |         "SOURCE" => &src,
98  | |         "BODY" => object!{
99  | |             "UUID" => reg_serial
100 | |         }
101 | |     };
    | |_____^ the trait `std::convert::From<&std::string::String>` is not implemented for `json::value::JsonValue`
    |
    = help: the following implementations were found:
              <json::value::JsonValue as std::convert::From<bool>>
              <json::value::JsonValue as std::convert::From<i8>>
              <json::value::JsonValue as std::convert::From<isize>>
              <json::value::JsonValue as std::convert::From<usize>>
            and 17 others
    = note: required because of the requirements on the impl of `std::convert::Into<json::value::JsonValue>` for `&std::string::String`
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: aborting due to previous error

[maciejhirsz]

Try src.as_str() instead of &src.

[ardawan]

Try src.as_str() instead of &src.

doesn't work. i got this error

src.as_str(),
    ^^^^^^ help: there is a method with a similar name: `as_ptr`

same for other data types. currently, I reach to the point that i need to pass the MutexGuard<'_, std::vec::Vec> type and i get this error.

107 |           "BODY" => object!{
    |  ___________________^
108 | |             "UUID" => peers[0].uuid,
109 | |             "PEERS" => peers,
110 | |         }
    | |_________^ the trait `std::convert::From<std::sync::MutexGuard<'_, std::vec::Vec<Peer>>>` is not implemented for `json::value::JsonValue`
    |
    = help: the following implementations were found:
              <json::value::JsonValue as std::convert::From<&'a str>>
              <json::value::JsonValue as std::convert::From<bool>>
              <json::value::JsonValue as std::convert::From<f32>>
              <json::value::JsonValue as std::convert::From<f64>>
            and 17 others
    = note: required because of the requirements on the impl of `std::convert::Into<json::value::JsonValue>` for `std::sync::MutexGuard<'_, std::vec::Vec<Peer>>`
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

[maciejhirsz]

1. What is the type of src? if it were a String you should be able to convert it to a str slice with .as_str().
2. Macro won't be able to handle a mutex guard for you, you need to get a raw Vec that satisfies the available From implementations for JsonValue. Just looking at the list now, regular slices are missing, so I can add that for convenience.

[ardawan]

1. What is the type of src? if it were a String you should be able to convert it to a str slice with .as_str().

The str is already a String type. that's why at first i just reference it rather than converting to str.

2. Macro won't be able to handle a mutex guard for you,...

I didn't know. is that only for this crate or is valid for all Macros in Rust ?

[maciejhirsz]

There is no implementation of From<&String> implemented, so you'll either have to convert it to &str manually, or clone it. The automatic conversion of &String -> &str happens only in function calls, not in macros, so that is a general thing. I can likely add that impl for convenience though.

Me not supporting mutex guards is just me, but in general there is a whole bunch of other pointers/containers you can wrap your values in (Arc, Rc, RefCell...), some of which might come from 3rd party crates, so as much as I'd like to expand the API here, things are much cleaner if I just allow a limited set of types that can automatically get cast to JsonValue inside the macro.