Boo: Explicitly specifying the type of a hash

boohashstatic-typing

I am new to Boo, and trying to figure out how to declare the type of a hash. When I do:

   myHash = {}
   myHash[key] = value
   (later)
   myHash[key].method()

the compiler complains that "method is not a member of object". I gather that it doesn't know what type the value in the hash is.

Is there any way I can declare to the compiler what type the keys and values of the hash are so that it won't complain?

Best Solution

The builtin hashtable in boo is very similar to the standard .NET Hashtable - the key and value of each entry are both of type "object".

Your best bet is to use a generic Dictionary:

import System.Collections.Generic

myHash = Dictionary[of string, Foo]()

This example will create a dictionary where the type of the key is a string, and the value will be of type Foo

Related Solutions

Perl – What’s the safest way to iterate through the keys of a Perl hash

The rule of thumb is to use the function most suited to your needs.

If you just want the keys and do not plan to ever read any of the values, use keys():

foreach my $key (keys %hash) { ... }

If you just want the values, use values():

foreach my $val (values %hash) { ... }

If you need the keys and the values, use each():

keys %hash; # reset the internal iterator so a prior each() doesn't affect the loop
while(my($k, $v) = each %hash) { ... }

If you plan to change the keys of the hash in any way except for deleting the current key during the iteration, then you must not use each(). For example, this code to create a new set of uppercase keys with doubled values works fine using keys():

%h = (a => 1, b => 2);

foreach my $k (keys %h)
{
  $h{uc $k} = $h{$k} * 2;
}

producing the expected resulting hash:

(a => 1, A => 2, b => 2, B => 4)

But using each() to do the same thing:

%h = (a => 1, b => 2);

keys %h;
while(my($k, $v) = each %h)
{
  $h{uc $k} = $h{$k} * 2; # BAD IDEA!
}

produces incorrect results in hard-to-predict ways. For example:

(a => 1, A => 2, b => 2, B => 8)

This, however, is safe:

keys %h;
while(my($k, $v) = each %h)
{
  if(...)
  {
    delete $h{$k}; # This is safe
  }
}

All of this is described in the perl documentation:

% perldoc -f keys
% perldoc -f each

Asp – How to configure an ASP.NET MVC project to work with Boo

So there are two levels of "work with Boo". One would be all the code (namely, the Controllers), and the other would be the views.

For the code, I assume Boo compiles to standard .NET assemblies, so simply properly following the naming conventions using by ASP.NET MVC should allow you to write Controllers. You will probably need to start with a C# or VB version of the MVC web application project template and port some of the boilerplate code over into Boo to get the solution entirely in Boo (I presume Boo supports Web Application projects?).

The other half is views. Someone will need to port the Brail view engine over to the ASP.NET MVC view engine system. This may already be done, but I don't know for sure. If it's not, then this is probably a significant amount of work to be done.

Probably the best place to get answers to these kinds of questions is the MvcContrib community on CodePlex.

Best Solution

Related Solutions

Perl – What’s the safest way to iterate through the keys of a Perl hash

Asp – How to configure an ASP.NET MVC project to work with Boo

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