Hi Silviu, Thanks for the example.
I have some questions popping up in my mind: Is my design wrong? Is your example and/or Roger's the most idiomatic way to do it in Go? Is it wrong to use type assertions in Go? Thanks. On Thursday, July 20, 2017 at 6:32:47 PM UTC+2, Silviu Capota Mera wrote: > > Hi Sofiane, > > Answering the "what type" question is pretty much unavoidable. > You can embed that forking logic inside the "on the fly" function, like in > Roger's example (using a switch v := v.(type) construct) or you can use > reflect. > > Alternatively, you can group your transformation functions into > functionality buckets, using maps: map[string]TFunc (where TFunc is > func(Valuer) Valuer like you wanted). > Each of your types (CSVString or CSVFloat, etc) would be "tied" to such a > map, returned by a new method in the Valuer interface: TFuncs() > map[string]TFunc > Quick example here: https://play.golang.org/p/ZnqJVw0Wzq > I just added some extra stuff to your code. I didn't bother trying to > understand if you wanted your rows mutated for each operation, or copied, > or such. That's your decision. > > For chaining transformers, please note that I changed your r := Row { ... > } to var r Transformer = &Row{ ... } > > Keep in mind that a lot of functional paradigms do not apply cleanly to > Go. For readability purposes, a simple for loop works wonders and it's > oftentimes more readable :) > > cheers, > silviu > > > > > On Thursday, 20 July 2017 07:58:09 UTC-4, rog wrote: >> >> I'm not convinced that holding all your values in a uniform way >> is going to be that helpful for you. You might be better using reflection >> to map the columns into a struct type (there's probably a package >> out there already that can do that). >> >> However, to answer without questioning the whole premise: >> >> You can't pass a function on a specific type to the more generally >> typed func(Valuer)Valuer because the value in the column might not >> be of the specific type - what should happen if the column is a string >> and you pass func(CSVFloat)CSVFloat to Apply? >> >> Here's your code made to work, with some arguably redundant stuff >> removed. The Transformer type seemed unnecessary, as Apply >> and RemoveColumn both work with the row in place. The Type field >> in the Column struct seemed unnecessary, as the type is implied by >> the value in the column. Also, the whole notion of Type seemed >> a bit redundant as CSV files have no notion of type, and it seems like >> you want to support custom types. The CSV prefix on the type names >> seemed unnecessary, as this would probably be in a package with >> some kind of csv-related name. >> >> https://play.golang.org/p/9mSfG1m4VZ >> >> cheers, >> rog. >> >> On 20 July 2017 at 08:05, Sofiane Cherchalli <sofi...@gmail.com> wrote: >> >>> Hi Silviu, >>> >>> Thanks for the reply. >>> >>> Basically I want to kinda functional map on my custom types by applying >>> functions on base value or struct values. >>> >>> What if I want to for instance: >>> >>> - Multiply the float64 value inside CSVFloat by 2 ? >>> - or Replace a custom type value with another one from the same type? >>> >>> Thanks >>> >>> >>> On Thursday, July 20, 2017 at 5:09:40 AM UTC+2, Silviu Capota Mera wrote: >>>> >>>> Before: myfn := func(v CSVFloat) CSVFloat { return v } >>>> >>>> After: myfn := func(v Valuer) Valuer { return v } >>>> >>>> On Wednesday, 19 July 2017 16:48:07 UTC-4, Sofiane Cherchalli wrote: >>>>> >>>>> Hi! >>>>> >>>>> I'm a noob in Go and I need some guidance/help on this: >>>>> https://play.golang.org/p/0TGzKiYQZn >>>>> >>>>> Basically I'm implementing a CSV parser, and applying transformations >>>>> on column value. >>>>> >>>>> In last part of the code I'm trying to apply a function on CSVFloat >>>>> type which satisfies Valuer interface, but I got a compiler error. >>>>> >>>>> In Scala language, this could be done by using map function, but how >>>>> to do it in Golang? >>>>> >>>>> Thanks. >>>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "golang-nuts" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to golang-nuts...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
