Thanks, Tim.
I understood my fault but still cannot get deserialization mixed value.
I tried to call pop method directly but it's private.
extern crate serialize;
use serialize::{Decodable, Decoder};
use serialize::json::{Json, Boolean, String, Null, I64, U64, F64};
use serialize::json;
#[deriving(Show)]
struct Primitive(Json);
impl<S: Decoder<E>, E> Decodable<S, E> for Primitive {
fn decode(decoder: &mut S) -> Result<Primitive, E> {
match decoder.pop() {
Null => Primitive(Null),
b @ Boolean(_)=> Primitive(b),
n @ I64(_) => Primitive(n),
n @ U64(_) => Primitive(n),
n @ F64(_) => Primitive(n),
s @ String(_) => Primitive(s),
bad => fail!("bad {}", bad)
}
}
}
On Thu, Sep 18, 2014 at 8:54 PM, Tim Joseph Dumol <t...@timdumol.com> wrote:
> Hi Daneel,
>
> What seems to be happening (which others might be able to confirm) is that
> the JSON decoder is consuming the string as a stack, and after the first
> read_int() fails, there is no nothing left to pop (in
> doc.rust-lang.org/src/serialize/home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libserialize/json.rs.html#1916),
> which causes the subsequent read_str() to fail. You can double-check this by
> removing the `read_int()` call, after which the `read_str()` works.
>
> Cheers,
>
> Tim Joseph Dumol
>
> On Fri, Sep 19, 2014 at 12:40 AM, Tim Joseph Dumol <t...@timdumol.com> wrote:
>>
>> Whoops, my bad! I misread your code in my haste to answer your question.
>> I'm a newbie to Rust, actually, so I'll have to spend some time exploring
>> why this is happening. Maybe someone else can help faster. Sorry for the
>> confusion!
>>
>> Tim Joseph Dumol
>>
>> On Fri, Sep 19, 2014 at 12:23 AM, Daneel Yaitskov
>> <rtfm.rtfm.r...@gmail.com> wrote:
>>>
>>> Why does read_str returns Result? I cannot catch the Err because of fail!
>>> It looks weird. Where is the sense?
>>>
>>> Just String result would better fit to read_str wiith such behavior,
>>> wouldn't it?
>>>
>>> Here is another question. Have Rust standard painless method to
>>> deserialize json map with different primitive value types (int, string,
>>> bool...)?
>>>
>>> json::decode(String) -> Option<HashMap<String,String>>
>>> or
>>> json::decode(String) -> Option<HashMap<String,Primitive>>
>>>
>>> where
>>> enum Primitive { Pint(int), Pstr(String), .... }
>>>
>>> On Sep 18, 2014 7:52 PM, "Tim Joseph Dumol" <t...@timdumol.com> wrote:
>>>>
>>>> Hi Daneel,
>>>>
>>>> Your `read_str` function tried to unwrap an `Option` that turned out to
>>>> be `None`, which caused your error. You'll want to `match` on the that
>>>> `Option` instead and handle for the case when it's a `None`. Good luck!
>>>>
>>>> Cheers,
>>>>
>>>> Tim Joseph Dumol
>>>>
>>>> On Thu, Sep 18, 2014 at 11:44 PM, Daneel Yaitskov
>>>> <rtfm.rtfm.r...@gmail.com> wrote:
>>>>>
>>>>> I have a custom json deserializer. It can parse string or number.
>>>>>
>>>>> json functions return Result enum so I guess if it fails it should
>>>>> return
>>>>> Err. But lines println!("crap") or println!("string is ok") are not
>>>>> reached.
>>>>>
>>>>> Program crashes with the following output:
>>>>>
>>>>> not int. let's try string
>>>>> task '<main>' failed at 'called `Option::unwrap()` on a `None` value',
>>>>> /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libcore/option.rs:278
>>>>>
>>>>>
>>>>> extern crate serialize;
>>>>> use serialize::{json, Decodable, Decoder};
>>>>>
>>>>> fn main() {
>>>>> let raw_json = "\"ddd\"";
>>>>> let person: Primitive = json::decode(raw_json).unwrap();
>>>>> println!("{}", person);
>>>>> }
>>>>>
>>>>> #[deriving(Show)]
>>>>> enum Primitive { ItInt(int), ItStr(String) }
>>>>>
>>>>> impl<S: Decoder<E>, E> Decodable<S, E> for Primitive {
>>>>> fn decode(decoder: &mut S) -> Result<Primitive, E> {
>>>>> match decoder.read_int() {
>>>>> Ok(n) => Ok(ItInt(n)),
>>>>> _ => {
>>>>> println!("not int. let's try string");
>>>>> match decoder.read_str() {
>>>>> Ok(s) => {
>>>>> println!("string is ok");
>>>>> Ok(ItStr(s))
>>>>> },
>>>>> _ => {
>>>>> println!("crap");
>>>>> Ok(ItStr("DDD".to_string()))
>>>>> }
>>>>> }
>>>>> }
>>>>> }
>>>>> }
>>>>> }
>>>>>
>>>>> --
>>>>> Daneel S. Yaitskov
>>>>>
>>>>> _______________________________________________
>>>>> Rust-dev mailing list
>>>>> Rust-dev@mozilla.org
>>>>> https://mail.mozilla.org/listinfo/rust-dev
>>>>>
>>>>
>>
>
--
Daneel S. Yaitskov
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