A best way to write this

Rails
1

I have a form, with 3 fields, then in my controller I get the paramters
to run a query but I don’t want to filter with paramters if they are
nil or blank…

I’m doing this
@condition = ‘’
if(params…)
@condition = @condition + " myparamter = " + params[…

if(params…)
@condition = @condition + " myparamter = " + params[…

if(params…)
@condition = @condition + " myparamter = " + params[…

but there is a best way to do this? more simple and more beautiful ?

tks

2

“Fernando” [email protected] wrote in
message news:[email protected]…

@condition = @condition + " myparamter = " + params[…

if(params…)
@condition = @condition + " myparamter = " + params[…

but there is a best way to do this? more simple and more beautiful ?

tks

[:param1, :param2, :param3].each do |p_name|
@condition += " myparameter=#{params[p_name]}" if params[p_name] &&
!params[p_name].empty?
end

needs polishing but that should give you some ideas

3

Fernando wrote:

I have a form, with 3 fields, then in my controller I get the paramters
to run a query but I don’t want to filter with paramters if they are
nil or blank…

I’m doing this
@condition = ‘’
if(params…)
@condition = @condition + " myparamter = " + params[…

if(params…)
@condition = @condition + " myparamter = " + params[…

if(params…)
@condition = @condition + " myparamter = " + params[…

but there is a best way to do this? more simple and more beautiful ?

tks

David A. Black’s book Ruby For Rails is pretty good at showing you cool
stuff. Throughout the book he uses this syntax:

@condition += params[:bleh] || “this :bleh is :blehnk”
the || means if params[:bleh] is nil then use “this :bleh is :blehnk”
the += means whatever is in condition now, put the following after it.
easier than doing @condition = @condition + … just do @condition +=
…

if you wanted to you could do it in 1 line:
@condition = "my parameter = " + (params[:bleh] || “this :bleh is
:blehnk”) + "my parameter2 = " + params[:bleh2] || “this :bleh2 is
:blehnk2” etc.

-Ben L.

4

Since blank? is a rails mixin that is true for empty and nil, I
believe this will work:

[:param1, :param2, :param3].each do |p_name|
@condition += " myparameter=#{params[p_name]}" unless params
[p_name].blank?
end

http://jlaine.net/articles/2006/06/14/hidden-rails-goodies-blank

        - dan

–
Dan K. mailto:[email protected]
http://www.dankohn.com/ tel:+1-415-233-1000

5

David A. Black’s book Ruby For Rails is pretty good at showing you cool
stuff. Throughout the book he uses this syntax:

@condition += params[:bleh] || “this :bleh is :blehnk”
the || means if params[:bleh] is nil then use “this :bleh is :blehnk”
the += means whatever is in condition now, put the following after it.
easier than doing @condition = @condition + … just do @condition +=
…

if you wanted to you could do it in 1 line:
@condition = "my parameter = " + (params[:bleh] || “this :bleh is
:blehnk”) + "my parameter2 = " + params[:bleh2] || “this :bleh2 is
:blehnk2” etc.

-Ben L.

forgot parenthesis on (params[:bleh2] || “this :bleh2 is :blehnk2”)

6

Fernando wrote:

@condition = @condition + " myparamter = " + params[…

if(params…)
@condition = @condition + " myparamter = " + params[…

but there is a best way to do this? more simple and more beautiful ?

Before worrying about simplicity and beauty, worry about correctness and
safety.

For correctness, you will need to put “AND” between the conditions you
are joining (and I’m sure they won’t all use the same “myparameter”).

For safety, you should not splice the value from params straight into
the conditions string. You should use the form of conditions with “?”
placeholders, and supply the arguments separately. Rails will then
ensure that the arguments are properly escaped before putting them into
the SQL.

http://api.rubyonrails.com/classes/ActiveRecord/Base.html#M000860

There has been some discussion of building conditions from multiple
parameters before in this list, and Ezra Z. produced the
ez_where plugin to make building such queries easy.

http://brainspl.at/articles/2006/06/30/new-release-of-ez_where-plugin

regards

Justin