How do I save a non-trivial value to an attribute in Elixir? -


so understand when defining attributes module in elixir syntax @myvariable 30 however, in case let's module defined follows:

defmodule mymodule    def add(x,y), do: x + y    @myvariable add(3,4)    def print, do: @myvariable end

ideally should print out 7, compileerror: undefined function add/2

in specific case, value want store attribute large map not trivial add(3,4) i'm pretty sure same concept applies. if attributes not correct way go this, please let me know real "elixir" way go is.

in case, i want able access keys of map throughout module instead of having pass whole map parameter each function.

thanks!

@values not variables, module attributes. not stored in module default , value exists during compile-time. elixir 'getting started' guide:

module attributes in elixir serve 3 purposes:

  1. they serve annotate module, information used user or vm.
  2. they work constants.
  3. they work temporary module storage used during compilation.

the problem code @myvariable being set during compilation of mymodule add(3, 4) can't calculated since module hasn't been compiled yet.

the simplest solution define add(x, y) in module , call there:

defmodule othermodule   def add(x, y), do: x + y end  defmodule mymodule   @myvariable othermodule.add(3, 4)   def print, do: @myvariable end

you can similarly define map module attribute, after compilation become constant won't able modify (which guess want).


Comments

Post a Comment

Popular posts from this blog

c# - Update a combobox from a presenter (MVP) -

i using mvp in project, new in mvp. have 2 comboboxes. when select option in combobox, combobox should filled new data. this action in presenter. view 'view1' in presenter, , introduced combobox1 , combobox2 properties in 'view1', because need 'datasource', 'displaymember', 'valuemember' , 'refresh()' in method below. but, when using pattern, enough send property like public string combobox2 { { return combobox1.selectedvalue.tosstring(); } } into presenter not whole combobox. how can solve problem? public void onselectedindexchangedcombobox1() { if (view1.combobox1.selectedindex == -1) { return; } datatable dt = tools.getdatatable("a path"); var query = (from o in dt.asenumerable() o.field<string>("afield") == farmerview.combobox1.selectedvalue.tostring() orderby o.field<string>("anotherfield") select...
Read more

How to understand 2 main() functions after using uftrace to profile the C++ program? -

i trying uftrace profile following simple c++ program: #include <iostream> class { public: a() {std::cout << "a created" << std::endl;} ~a() {std::cout << "a destroyed" << std::endl;} }; int main() { a; return 0; } the profile result this: # uftrace a.out created destroyed # duration tid function 2.026 [ 4828] | __cxa_atexit(); [ 4828] | main() { [ 4828] | __static_initialization_and_destruction_0() { 89.397 [ 4828] | std::ios_base::init::init(); 0.768 [ 4828] | __cxa_atexit(); 93.029 [ 4828] | } /* __static_initialization_and_destruction_0 */ 94.425 [ 4828] | } /* main */ [ 4828] | main() { [ 4828] | a::a() { 11.104 [ 4828] | std::operator <<(); 10.825 [ 4828] | std::basic_ostream::operator <<(); 24.514 [ 4828] | } /* a::a */ [ 4828] | a::~a() { 0.978 [ 4828] | ...
Read more

How to put a lock and transaction on table using spring 4 or above using jdbcTemplate and annotations like @Transactional? -

i trying put lock on table while writing on table , if happened in between roll-back . trying convert below code lock table test_g1 read; lock table test_g write; -- begin; start transaction; insert test_g1 values(143); insert test_g values(145); select * test_g1; select * test_g; rollback; select * test_g; unlock tables; how convert above code @transactional spring jdbctemplate code? @transactional(rollbackfor={dataaccessexception.class}) public void test(){ jdbctemplate.execute("insert test1 (id, nam) values (4, 'a')"); throw new dataaccessexception("error") { }; } here trying throw error, insert statement should rollback it's not happening . thanks edit-1 attaching code , doing in jdbcdaoimpl.java , mentioned problem comment above test() . app.java package com.cgiri.javabrains.spring4; import org.springframework.beans.factory.annotation.autowired; import org.springframework.context.applic...
Read more