I''d like to find all records that have a certain integer as their "level" field in the database. I know how to find all the records: allquestions = Question.find(:all) ...and I know how to find the one record that has a certain id: allquestions = Question.find(params[:id]) ...but how do you find all the records that share a certain value in one of their fields? I tried allquestions = Question.find(params[:level => 3]) ...but it just gave me an error. -- Posted via http://www.ruby-forum.com/.
sean colquhoun wrote:> I''d like to find all records that have a certain integer as their > "level" field in the database. I know how to find all the records: > > allquestions = Question.find(:all) > > ...and I know how to find the one record that has a certain id: > > allquestions = Question.find(params[:id]) > > ...but how do you find all the records that share a certain value in one > of their fields? I tried > > allquestions = Question.find(params[:level => 3]) > > ...but it just gave me an error.You want: allquestions = Question.find(:all, :conditions => "level = ''3'' ") Keep in mind that params[:whatever] calls data specifically from the params hash. (The contents of which you can see by forcing an error before you load a page. There''s probably a better way, but I haven''t read the Testing section of AWDWR. :P) -Adam -- Posted via http://www.ruby-forum.com/.
On Apr 6, 2006, at 11:56 PM, sean colquhoun wrote:> I''d like to find all records that have a certain integer as their > "level" field in the database. I know how to find all the records: > > allquestions = Question.find(:all) > > ...and I know how to find the one record that has a certain id: > > allquestions = Question.find(params[:id]) > > ...but how do you find all the records that share a certain value > in one > of their fields? I tried > > allquestions = Question.find(params[:level => 3]) > > ...but it just gave me an error.allquestions = Question.find(:all, :conditions => ''level = 3'') -- -- Tom Mornini
sean colquhoun wrote:> I''d like to find all records that have a certain integer as their > "level" field in the database. I know how to find all the records: > > allquestions = Question.find(:all) > > ...and I know how to find the one record that has a certain id: > > allquestions = Question.find(params[:id]) > > ...but how do you find all the records that share a certain value in one > of their fields? I tried > > allquestions = Question.find(params[:level => 3]) > > ...but it just gave me an error.Question.find(:all, :conditions => ''level = 3'') should work. / H -- Posted via http://www.ruby-forum.com/.
Adam Bloom wrote:> Keep in mind that params[:whatever] calls data specifically from the > params hash. (The contents of which you can see by forcing an error > before you load a page. There''s probably a better way, but I haven''t > read the Testing section of AWDWR. :P)You can use the "debug" helper: debug params With any object as an argument, debug will return information about it and its contents. Jeff -- Posted via http://www.ruby-forum.com/.
Thank you so much everybody. Workin'' like a charm now. -- Posted via http://www.ruby-forum.com/.
Wait. Spoke too soon. I can''t put a variable into where the ''3'' is in the above example. Is there a syntax that will let me set the condition as a variable or does it have to be hard-coded? -- Posted via http://www.ruby-forum.com/.
sean colquhoun wrote:> Wait. Spoke too soon. I can''t put a variable into where the ''3'' is in > the above example. Is there a syntax that will let me set the condition > as a variable or does it have to be hard-coded?There are two ways to accomplish what you''re trying to do. What I think is the better way is simply: allquestions = Question.find_all_by_level(params[:level]) However, if you want to use the :conditions option, with variable vallues, you can. You simply need to pass the conditions as an Array, like this: allquestions = Question.find(:all, :conditions => ["level = ?", params[:level]]) Each occurrence of "?" in the first item is replaced, in series, by the 2nd - nth items in the array. -Brian
Brian V. Hughes wrote:> > allquestions = Question.find(:all, > :conditions => ["level = ?", params[:level]]) > > Each occurrence of "?" in the first item is replaced, in series, by the > 2nd - > nth items in the array. > > -BrianThis is generally the preferred form, since although it might not make a difference in this particular case, in general it prevents SQL injection. See pg 440 of Agile Web Dev w/Rails. Keith -- Posted via http://www.ruby-forum.com/.
On Apr 7, 2006, at 8:49 AM, Keith Lancaster wrote:> Brian V. Hughes wrote: > >> >> allquestions = Question.find(:all, >> :conditions => ["level = ?", params[:level]]) >> >> Each occurrence of "?" in the first item is replaced, in series, >> by the >> 2nd - >> nth items in the array. >> >> -Brian > > This is generally the preferred form, since although it might not > make a > difference in this particular case, in general it prevents SQL > injection. See pg 440 of Agile Web Dev w/Rails.I''m quite sure Question.find_all_by_levels quotes the content as well, thereby avoiding SQL injection. -- -- Tom Mornini
Sorry guys - would it be possible to explain in a little more depth?
I''m
not sure how to implement your recommendations.
For example, if I use
allquestions = Question.find_all_by_level(params[:level]),
Is "find_all_by_level" some kind of dynamic method that I would need
to
change depending on the column name I use? i.e. if I want to pull
records out by "chapter", do I have to change the method call to
"find_all_by_chapter"? The Rails API didn''t have anything on
this. And,
I''m still shaky as to the difference between types of variables, for
example ''@variables'' vs. '':variables'' ? do I
have to set :level within
the controller or is that a value that I can pull out of my model?
...and then if I use
allquestions = Question.find(:all,
:conditions => ["level = ?", params[:level]])
Well, first of all, do I have to use this method with an array? All I
want to do is set a level in my model and then have the controller find
all the records that are of that level. I can''t think of any reason to
pass this thing more than one value, but I''m a total beginner too, so
there might be one that I can''t think of.
I guess also, since I don''t want to keep bothering people on this board
with simple stuff, if anybody knows of something online that will help
me understand things like how to know which variables are available to
which methods (variable scope?) and which ones aren''t, what exactly the
params[] array is and how to use it (also what it''s scope is), that
sort
of thing. I would be forever in your debt.
--
Posted via http://www.ruby-forum.com/.
On Apr 9, 2006, at 8:43 PM, sean colquhoun wrote:> I guess also, since I don''t want to keep bothering people on this > board > with simple stuff, if anybody knows of something online that will help > me understand things like how to know which variables are available to > which methods (variable scope?) and which ones aren''t, what exactly > the > params[] array is and how to use it (also what it''s scope is), that > sort > of thing. I would be forever in your debt.http://tinyurl.com/55oyg -- -- Tom Mornini
Tom Mornini wrote:> http://tinyurl.com/55oyg > > -- > -- Tom MorniniAlready have it, but it''s a meal of a book. If everything is in there, I''ll skip ahead and look for it. Thanks! -- Posted via http://www.ruby-forum.com/.
On Apr 9, 2006, at 11:43 PM, sean colquhoun wrote:> Sorry guys - would it be possible to explain in a little more > depth? I''m > not sure how to implement your recommendations.I''ll give it a try. Hopefully others will chime in if I miss something. ;)> For example, if I use > allquestions = Question.find_all_by_level(params[:level]), > > Is "find_all_by_level" some kind of dynamic method that I would > need to > change depending on the column name I use? i.e. if I want to pull > records out by "chapter", do I have to change the method call to > "find_all_by_chapter"?Yes, it''s a dynamic finder that allows you to specify one (or two) columns in a Model, upon which you want to perform a find. It''s very useful when the columns that you will be finding on don''t change, since as you pointed out, if you wanted to find on chapters, you would need to use a different dynamic finder.> The Rails API didn''t have anything on this. And, > I''m still shaky as to the difference between types of variables, for > example ''@variables'' vs. '':variables'' ? do I have to set :level within > the controller or is that a value that I can pull out of my model?Actually, I''m certain the Rails API, in the ActiveRecord::Base section covers dynamic finders quite thoroughly. I know because I''ve read through that section, more than once. :) But I learned about dynamic finders from the AWDwR book.> ...and then if I use > > allquestions = Question.find(:all, > :conditions => ["level = ?", params[:level]]) > > Well, first of all, do I have to use this method with an array?Do you have to? No. But if you are taking a item from the params object, which is actually set by the browser request, and funneling that directly into a find method, you become subject to a form of security exploit known as SQL Injection. Using the above format to build your find protects you from this exploit because it allows Rails to properly escape/quote the value that you want to use in your :conditions option.> All I want to do is set a level in my model and then have the > controller find all the records that are of that level. I can''t > think of any reason to pass this thing more than one value, but > I''m a total beginner too, so there might be one that I can''t think > of.Technically, you''re not passing it more than one value, but using the array form for :conditions is what you are supposed to do when you are dealing with a value that you don''t have a way to implicitly trust before you hand it off to Find for turning into an executable SQL statement. -Brian
>> The Rails API didn''t have anything on this. And, >> I''m still shaky as to the difference between types of variables, for >> example ''@variables'' vs. '':variables'' ? do I have to set :level within >> the controller or is that a value that I can pull out of my model? > > Actually, I''m certain the Rails API, in the ActiveRecord::Base > section covers dynamic finders quite thoroughly. I know because I''ve > read through that section, more than once. :) But I learned about > dynamic finders from the AWDwR book.Ha ha ha. Yeah, I forgot to include the disclaimer that I can''t read APIs, apparently. I was looking in the "methods" list because I thought it was a method. Whoops. -- Posted via http://www.ruby-forum.com/.
Ok.
:level = 2
allquestions = Question.find_all_by_level(params[:level])
is giving me
SyntaxError in <controller not set>#<action not set>
./script/../config/../app/controllers/test_controller.rb:26: parse
error, unexpected ''='', expecting kEND
:level = 2
^
Why can''t I set :level in the controller?
--
Posted via http://www.ruby-forum.com/.
sean colquhoun wrote:> Ok. > > :level = 2 > allquestions = Question.find_all_by_level(params[:level]) > > is giving me > > SyntaxError in <controller not set>#<action not set> > ./script/../config/../app/controllers/test_controller.rb:26: parse > error, unexpected ''='', expecting kEND > :level = 2 > ^ > > Why can''t I set :level in the controller?You might want to look into the Pickaxe Book ("Programming Ruby" by Dave Thomas), which covers basic Ruby concepts like variables and symbols. A name with a : before it is a symbol. That''s different from a variable, which is what you want in the example you''re giving. level = 2 allquestions = Question.find_all_by_level(level) You only need to use "params[:level]" if you''re using the parameters sent from another page, like a form. If you had a form on a search page, for example, with a dropdown list or an text field for the level value, then the number the user enters would be sent in the params hash with the :level key--params[:level]. If you just want to set a variable to search for some value explicitly, you can use a variable. If you''re just getting started with Rails, the "Agile Web Dev" book''s tutorial chapters are a great way to do it. Build the depot app from the book, and all this stuff gets covered. Jeff -- Posted via http://www.ruby-forum.com/.
> You might want to look into the Pickaxe Book ("Programming Ruby" by Dave > Thomas), which covers basic Ruby concepts like variables and symbols.Aha. For some reason I was under the impression that the :symbols were unique to Rails. That''s probably exactly what I need - I''ll look into it. Thanks. -- Posted via http://www.ruby-forum.com/.
sean colquhoun wrote:>> You might want to look into the Pickaxe Book ("Programming Ruby" by Dave >> Thomas), which covers basic Ruby concepts like variables and symbols. > > Aha. For some reason I was under the impression that the :symbols were > unique to Rails. That''s probably exactly what I need - I''ll look into > it. Thanks.There''s a discussion on the subject with some useful links in the Ruby mailing list (which I access through ruby-forum at http://www.ruby-forum.com/forum/4 ) in a subject called something like "What are symbols?", there should be some good info there too. Personally, I felt a bit overwhelmed by Rails'' syntax when I first started learning it, so I stepped back and spent some time with pure Ruby, writing a series of small applications to get the feel of the language. Once I was more comfortable with symbols, blocks, iterators, and Ruby in general, then I felt more confident diving into Rails. Jeff -- Posted via http://www.ruby-forum.com/.
Wow. So basically, symbols are not variables and also not strings. They can''t be set, but logically that seems like an invalid statement to me, since we can use the :id symbol from a form, and that obviously has been set, because it can return an integer like ''5'' and not just ''id''. If it could only return ''id'', it would be useless to any program unless that program was a program about the two letters ''i'' and ''d''. :-) So symbols aren''t set, but they can be, like, ''born'' (?) somehow or else they just exist perpetually. But it seems unclear how to control them. Holy jeez this is confusing. I think I''ll be investing in that Pickaxe Book soon. -- Posted via http://www.ruby-forum.com/.
sean colquhoun wrote:> Wow. So basically, symbols are not variables and also not strings. They > can''t be set, but logically that seems like an invalid statement to me, > since we can use the :id symbol from a form, and that obviously has been > set, because it can return an integer like ''5'' and not just ''id''. If it > could only return ''id'', it would be useless to any program unless that > program was a program about the two letters ''i'' and ''d''. > > :-) > > So symbols aren''t set, but they can be, like, ''born'' (?) somehow or else > they just exist perpetually. But it seems unclear how to control them. > Holy jeez this is confusing. I think I''ll be investing in that Pickaxe > Book soon.It''s worth every penny. :) Jeff -- Posted via http://www.ruby-forum.com/.
>>>>> "sean" == sean colquhoun <seancolquhoun@gk-a.com> writes:> Wow. So basically, symbols are not variables and also not strings.Exactly. They are symbols. You can think of them as free-floating names, in a way.> They can''t be set, but logically that seems like an invalid > statement to me, since we can use the :id symbol from a form, and > that obviously has been set, because it can return an integer like > ''5'' and not just ''id''.No, you have misunderstood here. Parameters from a form come to your controller in the form of a hash. When you write params[:id], you''re just using the :id symbol as a key into that hash, and you get the value 5 back. :id has no value other than :id, but the params hash has a value keyed to the name :id. Do you see the difference?> Holy jeez this is confusing. I think I''ll be investing in that > Pickaxe Book soon.That would probably be an excellent idea, yes. Knowing Ruby makes it a wee bit easier to program in Ruby, to put it mildly. But if you really want to get into the concept and use of symbols in programming languages, you should study Lisp :-) -- Calle Dybedahl <calle@cyberpomo.com> http://www.livejournal.com/users/cdybedahl/ "Last week was a nightmare, never to be repeated - until this week" -- Tom, a.s.r
> But if you really want to get into the concept and use of symbols in > programming languages, you should study Lisp :-)Thanks. You cleared that up for me. Unfortunately, however, I graduated with a degree in graphic arts and the most challenging thing I''ve done so far was program a mini-CMS for myself (ha ha ha-one page only-but it does the trick) in PHP. OOP is something of a leap for me. i''m going to have to take it one tongue at a time for the time being. ;-) -- Posted via http://www.ruby-forum.com/.