How can I test an object's other-trait functions
0
I have a Template struct implementing a encoder function that returns a reference to a Boxed Encoder.
I also have a FixedEncoder struct that implements Encoder
I can create the Template and get the Encoder out, but how do I test the functions of FixedEncoder? I'm only looking to get FixedEncoder for testing purposes, so "unsafe" solutions are fine (though safe ones are preferred)
In my following example I get the error
error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
Example (playground):
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template {
Template { encoder }
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
assert_eq!(&template.encoder().length(), 1); // error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
}
rust
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
add a comment |
0
I have a Template struct implementing a encoder function that returns a reference to a Boxed Encoder.
I also have a FixedEncoder struct that implements Encoder
I can create the Template and get the Encoder out, but how do I test the functions of FixedEncoder? I'm only looking to get FixedEncoder for testing purposes, so "unsafe" solutions are fine (though safe ones are preferred)
In my following example I get the error
error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
Example (playground):
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template {
Template { encoder }
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
assert_eq!(&template.encoder().length(), 1); // error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
}
rust
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
2
It isn't possible to "cast" one trait object into another. Probably a more idiomatic approach would be to use anenumof the possible encoders, rather than traits.
– E4_net_or_something_like_that
Nov 14 '18 at 20:45
2
For example: play.rust-lang.org/…
– E4_net_or_something_like_that
Nov 14 '18 at 20:55
@PeterHall thanks! I'll try integrating and see if it works out. Very much appreciated
– Aakil Fernandes
Nov 14 '18 at 21:03
1
This answer may help to explain why you can't cast between traits - even if you know the type implements them: stackoverflow.com/a/25247480/493729
– E4_net_or_something_like_that
Nov 14 '18 at 21:04
@PeterHall thanks for the link. I was aware of the inability to cast between traits and sorta understand why (that link certainly helps). I was looking for a workaround an I think the enum solution you provided should work (integrating now).
– Aakil Fernandes
Nov 14 '18 at 21:14
add a comment |
0
0
0
I have a Template struct implementing a encoder function that returns a reference to a Boxed Encoder.
I also have a FixedEncoder struct that implements Encoder
I can create the Template and get the Encoder out, but how do I test the functions of FixedEncoder? I'm only looking to get FixedEncoder for testing purposes, so "unsafe" solutions are fine (though safe ones are preferred)
In my following example I get the error
error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
Example (playground):
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template {
Template { encoder }
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
assert_eq!(&template.encoder().length(), 1); // error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
}
rust
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
I have a Template struct implementing a encoder function that returns a reference to a Boxed Encoder.
I also have a FixedEncoder struct that implements Encoder
I can create the Template and get the Encoder out, but how do I test the functions of FixedEncoder? I'm only looking to get FixedEncoder for testing purposes, so "unsafe" solutions are fine (though safe ones are preferred)
In my following example I get the error
error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
Example (playground):
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template {
Template { encoder }
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
assert_eq!(&template.encoder().length(), 1); // error[E0599]: no method named `length` found for type `&std::boxed::Box<(dyn Encoder + 'static)>` in the current scope
}
rust
rust
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
edited Nov 14 '18 at 21:06
E4_net_or_something_like_that
16.7k74388
16.7k74388
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
asked Nov 14 '18 at 19:53
Aakil FernandesAakil Fernandes
3,58232040
3,58232040
2
It isn't possible to "cast" one trait object into another. Probably a more idiomatic approach would be to use anenumof the possible encoders, rather than traits.
– E4_net_or_something_like_that
Nov 14 '18 at 20:45
2
For example: play.rust-lang.org/…
– E4_net_or_something_like_that
Nov 14 '18 at 20:55
@PeterHall thanks! I'll try integrating and see if it works out. Very much appreciated
– Aakil Fernandes
Nov 14 '18 at 21:03
1
This answer may help to explain why you can't cast between traits - even if you know the type implements them: stackoverflow.com/a/25247480/493729
– E4_net_or_something_like_that
Nov 14 '18 at 21:04
@PeterHall thanks for the link. I was aware of the inability to cast between traits and sorta understand why (that link certainly helps). I was looking for a workaround an I think the enum solution you provided should work (integrating now).
– Aakil Fernandes
Nov 14 '18 at 21:14
add a comment |
2
It isn't possible to "cast" one trait object into another. Probably a more idiomatic approach would be to use anenumof the possible encoders, rather than traits.
– E4_net_or_something_like_that
Nov 14 '18 at 20:45
2
For example: play.rust-lang.org/…
– E4_net_or_something_like_that
Nov 14 '18 at 20:55
@PeterHall thanks! I'll try integrating and see if it works out. Very much appreciated
– Aakil Fernandes
Nov 14 '18 at 21:03
1
This answer may help to explain why you can't cast between traits - even if you know the type implements them: stackoverflow.com/a/25247480/493729
– E4_net_or_something_like_that
Nov 14 '18 at 21:04
@PeterHall thanks for the link. I was aware of the inability to cast between traits and sorta understand why (that link certainly helps). I was looking for a workaround an I think the enum solution you provided should work (integrating now).
– Aakil Fernandes
Nov 14 '18 at 21:14
2
2
It isn't possible to "cast" one trait object into another. Probably a more idiomatic approach would be to use an
enum of the possible encoders, rather than traits.– E4_net_or_something_like_that
Nov 14 '18 at 20:45
It isn't possible to "cast" one trait object into another. Probably a more idiomatic approach would be to use an
enum of the possible encoders, rather than traits.– E4_net_or_something_like_that
Nov 14 '18 at 20:45
2
2
For example: play.rust-lang.org/…
– E4_net_or_something_like_that
Nov 14 '18 at 20:55
For example: play.rust-lang.org/…
– E4_net_or_something_like_that
Nov 14 '18 at 20:55
@PeterHall thanks! I'll try integrating and see if it works out. Very much appreciated
– Aakil Fernandes
Nov 14 '18 at 21:03
@PeterHall thanks! I'll try integrating and see if it works out. Very much appreciated
– Aakil Fernandes
Nov 14 '18 at 21:03
1
1
This answer may help to explain why you can't cast between traits - even if you know the type implements them: stackoverflow.com/a/25247480/493729
– E4_net_or_something_like_that
Nov 14 '18 at 21:04
This answer may help to explain why you can't cast between traits - even if you know the type implements them: stackoverflow.com/a/25247480/493729
– E4_net_or_something_like_that
Nov 14 '18 at 21:04
@PeterHall thanks for the link. I was aware of the inability to cast between traits and sorta understand why (that link certainly helps). I was looking for a workaround an I think the enum solution you provided should work (integrating now).
– Aakil Fernandes
Nov 14 '18 at 21:14
@PeterHall thanks for the link. I was aware of the inability to cast between traits and sorta understand why (that link certainly helps). I was looking for a workaround an I think the enum solution you provided should work (integrating now).
– Aakil Fernandes
Nov 14 '18 at 21:14
add a comment |
1 Answer
1
active
oldest
votes
0
I was able to accomplish this by using Any.
- Add an
as_anydeclaration toEncoder
- Add an
as_anyfunction toFixedEncoder
- Use
.as_any().downcast_ref().unwrap()on the retreivedEncoder
playground
use std::any::Any;
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template{
Template {
encoder
}
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
fn as_any(&self) -> &dyn Any;
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {
fn as_any(&self) -> &dyn Any {
self
}
}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
let fixed_encoder_from_template : &FixedEncoder = &template.encoder().as_any().downcast_ref().unwrap();
assert_eq!(&fixed_encoder_from_template.length, &(1 as usize));
}
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
add a comment |
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1 Answer
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1 Answer
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oldest
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0
I was able to accomplish this by using Any.
- Add an
as_anydeclaration toEncoder
- Add an
as_anyfunction toFixedEncoder
- Use
.as_any().downcast_ref().unwrap()on the retreivedEncoder
playground
use std::any::Any;
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template{
Template {
encoder
}
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
fn as_any(&self) -> &dyn Any;
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {
fn as_any(&self) -> &dyn Any {
self
}
}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
let fixed_encoder_from_template : &FixedEncoder = &template.encoder().as_any().downcast_ref().unwrap();
assert_eq!(&fixed_encoder_from_template.length, &(1 as usize));
}
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
add a comment |
0
I was able to accomplish this by using Any.
- Add an
as_anydeclaration toEncoder
- Add an
as_anyfunction toFixedEncoder
- Use
.as_any().downcast_ref().unwrap()on the retreivedEncoder
playground
use std::any::Any;
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template{
Template {
encoder
}
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
fn as_any(&self) -> &dyn Any;
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {
fn as_any(&self) -> &dyn Any {
self
}
}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
let fixed_encoder_from_template : &FixedEncoder = &template.encoder().as_any().downcast_ref().unwrap();
assert_eq!(&fixed_encoder_from_template.length, &(1 as usize));
}
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
add a comment |
0
0
0
I was able to accomplish this by using Any.
- Add an
as_anydeclaration toEncoder
- Add an
as_anyfunction toFixedEncoder
- Use
.as_any().downcast_ref().unwrap()on the retreivedEncoder
playground
use std::any::Any;
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template{
Template {
encoder
}
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
fn as_any(&self) -> &dyn Any;
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {
fn as_any(&self) -> &dyn Any {
self
}
}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
let fixed_encoder_from_template : &FixedEncoder = &template.encoder().as_any().downcast_ref().unwrap();
assert_eq!(&fixed_encoder_from_template.length, &(1 as usize));
}
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
I was able to accomplish this by using Any.
- Add an
as_anydeclaration toEncoder
- Add an
as_anyfunction toFixedEncoder
- Use
.as_any().downcast_ref().unwrap()on the retreivedEncoder
playground
use std::any::Any;
pub struct Template {
encoder: Box<Encoder>
}
impl Template {
fn new(encoder: Box<Encoder>) -> Template{
Template {
encoder
}
}
fn encoder(&self) -> &Box<Encoder> {
&self.encoder
}
}
pub trait Encoder {
fn isEncoder(&self) -> bool {
true
}
fn as_any(&self) -> &dyn Any;
}
pub struct FixedEncoder {
length: usize
}
impl FixedEncoder {
pub fn new(length: usize) -> FixedEncoder {
FixedEncoder { length }
}
pub fn length(&self) -> usize {
self.length
}
}
impl Encoder for FixedEncoder {
fn as_any(&self) -> &dyn Any {
self
}
}
fn main() {
let fixed_encoder = FixedEncoder::new(1);
let template = Template::new(Box::new(fixed_encoder));
assert_eq!(template.encoder().isEncoder(), true); // works
let fixed_encoder_from_template : &FixedEncoder = &template.encoder().as_any().downcast_ref().unwrap();
assert_eq!(&fixed_encoder_from_template.length, &(1 as usize));
}
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
answered Nov 14 '18 at 23:18
Aakil FernandesAakil Fernandes
3,58232040
3,58232040
add a comment |
add a comment |
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2
It isn't possible to "cast" one trait object into another. Probably a more idiomatic approach would be to use an
enumof the possible encoders, rather than traits.– E4_net_or_something_like_that
Nov 14 '18 at 20:45
2
For example: play.rust-lang.org/…
– E4_net_or_something_like_that
Nov 14 '18 at 20:55
@PeterHall thanks! I'll try integrating and see if it works out. Very much appreciated
– Aakil Fernandes
Nov 14 '18 at 21:03
1
This answer may help to explain why you can't cast between traits - even if you know the type implements them: stackoverflow.com/a/25247480/493729
– E4_net_or_something_like_that
Nov 14 '18 at 21:04
@PeterHall thanks for the link. I was aware of the inability to cast between traits and sorta understand why (that link certainly helps). I was looking for a workaround an I think the enum solution you provided should work (integrating now).
– Aakil Fernandes
Nov 14 '18 at 21:14