crystal-lang/crystal

The Crystal programming language | http://crystal-lang.org | Fund Crystal's development: http://is.gd/X7PRtI | Docs: http://crystal-lang.org/docs/ | API: http://crystal-lang.org/api/

Zafar Ansari

@ansarizafar

how can I run list method which is store in a hash

Ghost

@ghost~55586c4815522ed4b3e08557

do you need to pass arguments to thoses methods when calling them?

Zafar Ansari

@ansarizafar

yes

Ghost

@ghost~55586c4815522ed4b3e08557

are they known when you add the method to the hash?

Zafar Ansari

@ansarizafar

Ary Borenszweig

@asterite

case key; when "list" then User.list; etc.

Zafar Ansari

@ansarizafar

I want to make it generic. Is there any syntax that I can use to run the method stored in hash directly.

Jason Waldrip

@jwaldrip

Can the proc/method return any type?

Zafar Ansari

@ansarizafar

Ideally I would like to store a proc block in hash without specifying return type as return type is not known in advance, but I think its not possible.

Jason Waldrip

@jwaldrip

If you know what the possible types could be you could store them in a union

Zafar Ansari

@ansarizafar

Like that

@@store = {} of String => (Hash(String, JSON::Type) -> _)

Jason Waldrip

@jwaldrip

or, let me ask a question... do you expect your method to always return something?

Or are you just trying to invoke a method that may just invoke something, not nessicarily return something?

Ghost

@ghost~55586c4815522ed4b3e08557

@ansarizafar do you need the return value when calling it?

Zafar Ansari

@ansarizafar

yes, It could be a NameTuple or an Array Of NamedTuples

Jason Waldrip

@jwaldrip

So use a union

Zafar Ansari

@ansarizafar

Yes I need return value

Jason Waldrip

@jwaldrip

If you know the various return types, just set it up as a union

Zafar Ansari

@ansarizafar

Return types are not known in advance. Namedtuple will be generated with the fields returned from Postgre Db depending on the query.

Will

@Willamin

Hi everyone! I've got an absolutely crazy question for you. I want to reopen the Integer structs and add a macro def that throws a compile time exception based on the value of the Integer. I can't find a definitive list of macro variables such as @type and @def. Can anyone here help?

Ghost

@ghost~55586c4815522ed4b3e08557

throw a compile time error when doing what @Willamin ?

Will

@Willamin

Contrived example: I'd like to add a .is_this_a_0_at_compile_time to Integers that throws a compile time error if it's called on a non-zero integer

0.is_this_a_0_at_compile_time # should compile fine
1.is_this_a_0_at_compile_time # should throw a compile time error

Ghost

@ghost~55586c4815522ed4b3e08557

how is this supposed to be used?

Zafar Ansari

@ansarizafar

Here is my current code

module WebWare
  abstract class Method
    abstract def call(args)
  end

  class Api
    @@store = {} of String => Method

    def initialize
    end
    def self.register(name : String, method : Method)
      @@store[name] = method
    end

    def self.run(context : HTTP::Server::Context)
      begin
        data = Tools.json_param(context)
        finalResult = data.map do |key, value|
          {key => @@store[key].call(value.as(Hash))}
        end

        return finalResult.to_json
      rescue ex
        # context.response.respond_with_error("Internal error", 500)
        "Internal error in Method"
      end
    end
  end
end

Ghost

@ghost~55586c4815522ed4b3e08557

The syntax you ask is not possible because macros are not methods with a receiver, they're on the class/module/top level, not instance level, but you could have is_this_a_0_at_compile_time(0) quite easily @Willamin

Zafar Ansari

@ansarizafar

Here is User class

include WebWare

class Users < Method
  def call(args)
    begin
      count = Db.scalar "select count(*) from restock.users"
      data = [] of {id: String, name: String}

      Db.query "select id, name from restock.users" do |rs|
        rs.each do
          id, name = rs.read(String, String)
          data << {id: id, name: name}
        end
      end

      {success: true, data: data}
    rescue ex
      {success: false, data: [] of {id: String, name: String}}
    end
  end
end

Api.register "user.list", Users.new

Will

@Willamin

@bew even when it's a macro on a literal struct like an Int32?

From IRC (bridge bot)

@FromIRC

<oprypin> @eliasjpr, do u have rights to sell Crystal logo?

Ghost

@ghost~55586c4815522ed4b3e08557

yes, if you write a macro my_macro in Int32's struct, you'll be able to call it as Int32.my_macro or just my_macro when called in the scope of the Int32 struct

From IRC (bridge bot)

@FromIRC

<Papierkorb> William, how should the program know at compile-time, which run-time value the integer will have?

<Papierkorb> Crystal isn't a time machine

Ghost

@ghost~55586c4815522ed4b3e08557

\o/

Will

@Willamin

hahaha

From IRC (bridge bot)

@FromIRC

<Papierkorb> A method that takes an integer (or anything) as argument doesn't know if it was passed in as literal or through an variable (or ...), if that's what you mean.

Will

@Willamin

I was hoping that I would also be able to tell if the macro was called from a literal (eg. 0.is_this_a_0_at_compile_time) vs called from a variable (eg. x.is_this_a_0_at_compile_time),

From IRC (bridge bot)

@FromIRC

<Papierkorb> No, as a macro is state-less, you can't call it like a member method.

Ghost

@ghost~55586c4815522ed4b3e08557

@Willamin https://carc.in/#/r/2sqz

Will

@Willamin

You can call a macro like a member method, using macro def, can you not?

From IRC (bridge bot)

@FromIRC

<Papierkorb> But a macro, if you pass it as argument to it, can know if it's a literal or not, and then could signal an error to the user

Ghost

@ghost~55586c4815522ed4b3e08557

@Willamin macro def is not really documented iirc, it's not meant for this use I think

From IRC (bridge bot)

@FromIRC

<Papierkorb> https://crystal-lang.org/docs/syntax_and_semantics/macros/macro_methods.html in fact it is documented

<Papierkorb> With a disclaimer

Ghost

@ghost~55586c4815522ed4b3e08557

ah thanks

either way, in a macro def you have access to @type (Int32) but not self (0) at compile time

Will

@Willamin

Oh well, thanks anyways! :D

Serdar Dogruyol - Sedo セド

@sdogruyol

how can I check if a value is truthy outside of a guard clause

From IRC (bridge bot)

@FromIRC

<Yxhuvud> What do you want to achieve?

Elias Perez

@eliasjpr

@oprypin My apologies was never my intention I will remove

I just wanted some tees

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