Re: [go-nuts] Extension for type assertion of interface array

[nsakthi93]

Type assertion is not required in the given example (from array of structs 
to interface), But you need to assert if array of one interface is type 
casted to array of another interface. I started this thread to know whether 
this pattern requires a language level change to avoid unwanted array copy 
and code duplication for similar pattern of code. I agree that there are 
many ways in Golang to make this code run but shouldn't the language 
provide an extension to already available syntax to address this in simple 
and elegant way?


On Thursday, 19 April 2018 21:36:38 UTC+5:30, Jake Montgomery wrote:
>
> Yes, to use the functions above you will need to copy the slices of 
> landSpaceto slices of the respective interface types. But I you do not 
> need to do any type assertions. Like this: 
>
> https://play.golang.org/p/eFTUqpImyPc
> package main
>
> import (
> "fmt"
> )
>
> type landSpace struct{}
>
> func (*landSpace) Foo() {
> fmt.Println("Foo")
> }
>
> func (*landSpace) Bar() {
> fmt.Println("Bar")
> }
>
> type Shape interface {
> Foo()
> }
>
> type Property interface {
> Bar()
> }
>
> var a []*landSpace
>
> func processShapes(shapes []Shape) {
> for _, s := range shapes {
> s.Foo()
> }
> }
>
> func evaluateProperties(properties []Property) {
> for _, p := range properties {
> p.Bar()
> }
> }
>
> func main() {
> a = append(a, {}, {})
>
> var shapes []Shape
> for _, l := range a {
> shapes = append(shapes, l)
> }
> processShapes(shapes)
>
> var properties []Property
> for _, l := range a {
> properties = append(properties, l)
> }
> evaluateProperties(properties)
> fmt.Println("Hello, playground")
> }
>
> Is this what you meant? I see how something like shapes = a.([]Shape) would 
> be convenient to avoid having to do an explicit conversion. Hoever, until 
> Go has some form of generics,  it seems unlikely. Keep in mind that a Shape 
> and *landSpace are two different types, with different in memory 
> representations. So to avoid major language changes, the type assertion 
> would have to create a new slice anyway.
>
>
> On Thursday, April 19, 2018 at 12:59:12 AM UTC-4, Sakthi Natesan wrote:
>>
>> Usescases that I came across doesn't involve []interface{}. 
>>
>> My usecases will be similar to this sample code 
>> 
>>
>> type landSpace struct {
>> //consider that landSpace implements all functions from both Shape and 
>> property interfaces
>> ...
>> }
>> type Shape interface {
>> ...
>> }
>>
>>
>> type property interface {
>>
>> ...
>> }
>>
>>
>> var a []*landSpace
>>
>> func processShapes(shapes []Shape) {
>> //
>> }
>>
>> func evaluateProperties(properties []Property) {
>> //
>> }
>>
>>
>>
>> If I want to pass the variable 'a' to both the functions, then I have to 
>> write two functions to clone and typeAssert to respective interfaces.
>>
>>
>> On Wednesday, 18 April 2018 19:53:33 UTC+5:30, Jan Mercl wrote:
>>>
>>> On Wed, Apr 18, 2018 at 4:13 PM  wrote:
>>>
>>> When possible, avoid using '[]interface{}' and use just 'interface{}' 
>>> instead: https://play.golang.org/p/oPtPoGChkMZ.
>>>
>>>
>>> -- 
>>>
>>> -j
>>>
>>

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Re: [go-nuts] Extension for type assertion of interface array

[nsakthi93]

Usescases that I came across doesn't involve []interface{}. 

My usecases will be similar to this sample code 


type landSpace struct {
//consider that landSpace implements all functions from both Shape and 
property interfaces
...
}
type Shape interface {
...
}


type property interface {

...
}


var a []*landSpace

func processShapes(shapes []Shape) {
//
}

func evaluateProperties(properties []Property) {
//
}



If I want to pass the variable 'a' to both the functions, then I have to 
write two functions to clone and typeAssert to respective interfaces.


On Wednesday, 18 April 2018 19:53:33 UTC+5:30, Jan Mercl wrote:
>
> On Wed, Apr 18, 2018 at 4:13 PM  wrote:
>
> When possible, avoid using '[]interface{}' and use just 'interface{}' 
> instead: https://play.golang.org/p/oPtPoGChkMZ.
>
>
> -- 
>
> -j
>

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[go-nuts] Extension for type assertion of interface array

[nsakthi93]

Go supports below type assertion 

t := i.(T)
and 
t, ok := i.(T)

Can this feature be extended to array of interfaces as mentioned below?

t := i.([]T)
and 
t, ok := i.([]T)


I have been using Golang for almost four years and I have come across use 
cases requiring this feature many times. So far, I write a function for 
each specific case which clones the array into new array with type asserted 
to new type. I repeat the same pattern of assertion for array of different 
types and perform extra array copy each time I assert. Is there a better 
alternative solution with existing Go feature or Is there a chance that 
this feature will be supported in future?

sample code 

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