Try:

    &lt;%= link_to &quot;Add to cart&quot;, {:controller =&gt; &quot;car&quot;, :action =&gt; &quot;add_to_cart&quot;, :car =&gt; car.id }%&gt;

and then in your controller

    @car = Car.find(params[:car])

which, will find in your &#39;cars&#39; table  (as with rails pluralization) in your DB a car with id == to car.id

hope it helps! happy coding

more than a year later, but if you see it or anyone does, i could use the points ;D

The above did not work for me but **this** did

`&lt;%= link_to &quot;text_to_show_in_url&quot;, action_controller_path(:gender =&gt; &quot;male&quot;, :param2=&gt; &quot;something_else&quot;) %&gt;`

Maybe try this:

    &lt;%= link_to &quot;Add to cart&quot;, 
                :controller =&gt; &quot;car&quot;, 
                :action =&gt; &quot;add_to_cart&quot;, 
                :car =&gt; car.attributes %&gt;

But I&#39;d really like to see where the car object is getting setup for this page (i.e., the rest of the view).

You probably don&#39;t want to pass the `car` object as a parameter, try just passing `car.id`.  What do you get when you `inspect(params)` after clicking &quot;Add to cart&quot;?

If I have two parallel lists and want to sort them by the order of the elements in the first, it&#39;s very easy:

    &gt;&gt;&gt; a = [2, 3, 1]
    &gt;&gt;&gt; b = [4, 6, 7]
    &gt;&gt;&gt; a, b = zip(*sorted(zip(a,b)))
    &gt;&gt;&gt; print a
    (1, 2, 3)
    &gt;&gt;&gt; print b
    (7, 4, 6)

How can I do the same using numpy arrays without unpacking them into conventional Python lists?

How can I &quot;zip sort&quot; parallel numpy arrays?

Why is it a bad design for an object to refer to another object that refers back to the first one?

Why are circular references considered harmful?

I have this line of code:

    &lt;%= link_to &quot;Add to cart&quot;, :controller =&gt; &quot;car&quot;, :action =&gt; &quot;add_to_cart&quot;, :car =&gt; car %&gt;


when im in the add_to_cart method...how can i call the :car please?


    @car = Car.new(params[:car])

That doesn&#39;t work because it says that I&#39;m trying to stringify it.

I don&#39;t understand what&#39;s wrong; because I used this to create new users and it worked fine.

By the way, car is my car object.


 

pass parameter by link_to ruby on rails

I have this line of code:
<pre><code class="hljs language-javascript">&#x3C;%= link_to "Add to cart", :controller => "car", :action => "add_to_cart", :car => car %>
</code></pre>
when im in the add_to_cart method...how can i call the :car please?
<pre><code class="hljs language-csharp">@car = Car.new(params[:car])
</code></pre>
That doesn't work because it says that I'm trying to stringify it.
I don't understand what's wrong; because I used this to create new users and it worked fine.
By the way, car is my car object.

I would like to raise an exception so that it does the same thing a normal Rails exception does. Specially, show the exception and stack trace in development mode and show &quot;We&#39;re sorry, but something went wrong&quot; page in production mode. 

I tried the following:

    raise &quot;safety_care group missing!&quot; if group.nil?

But it simply writes `&quot;ERROR signing up, group missing!&quot;` to the development.log file


How do I raise an exception in Rails so it behaves like other Rails exceptions?

I want the primary key values to start from 1 again.

How to reset a single table in rails?

I have user entries as filenames. Of course this is not a good idea, so I want to drop everything except `[a-z]`, `[A-Z]`, `[0-9]`, `_` and `-`. 

For instance:

    my&#167;document$is&#176;&#176;   very&amp;interesting___thisIs%nice445.doc.pdf

should become

    my_document_is_____very_interesting___thisIs_nice445_doc.pdf

and then ideally

    my_document_is_very_interesting_thisIs_nice445_doc.pdf

Is there a nice and elegant way for doing this?

How to make a Ruby string safe for a filesystem?

I can&#39;t seem to find the syntax to add a class to a select tag generated by Rails [`collection_select`][1]. Some help?


  [1]: http://apidock.com/rails/ActionView/Helpers/FormOptionsHelper/collection_select

How do I set the HTML options for collection_select in Rails?

How can I change my Rails application to run in production mode? Is there a config file, environment.rb for example, to do that?


Change a Rails application to production

Is there a way to set up a C# function to accept any number of parameters? For example, could you set up a function such that the following all work - 

    x = AddUp(2, 3)
    
    x = AddUp(5, 7, 8, 2)
    
    x = AddUp(43, 545, 23, 656, 23, 64, 234, 44)

Pass multiple optional parameters to a C# function

I&#39;m wondering whether to use matrix or query parameters in my URLs. I found an older [discussion][1] to that topic not satisfying.

Examples

- URL with query params: http://some.where/thing?paramA=1&amp;paramB=6542
- URL with matrix params: http://some.where/thing;paramA=1;paramB=6542

At first sight matrix params seem to have only advantages:

 - more readable
 - no encoding and decoding of &quot;&amp;&quot; in XML documents is required
 - URLs with &quot;?&quot; are not cached in many cases; URLs with matrix params are cached
 - matrix parameters can appear everywhere in the path and are not limited to its end
 - matrix parameters can have more than one value: `paramA=val1,val2`
 
But there are also disadvantages:

 - only a few frameworks like [JAX-RS][2] support matrix parameters
 - When a browser submits a form via GET, the params become query params. So it ends up in two kinds of parameters for the same task. To not confuse users of the REST services and limit the effort for the developers of the services, it would be easier to use always query params - in this area.

Since the developer of the service can choose a framework with matrix param support, the only remaining disadvantage would be that browsers create by default query parameters.

Are there any other disadvantages? What would you do?


  [1]: https://stackoverflow.com/questions/401981/when-to-use-query-parameters-versus-matrix-parameters
  [2]: https://jsr311.dev.java.net/

URL matrix parameters vs. query parameters

I&#39;ve got a R script for which I&#39;d like to be able to supply several command-line parameters (rather than hardcode parameter values in the code itself).  The script runs on Windows.

I can&#39;t find info on how to read parameters supplied on the command-line into my R script.  I&#39;d be surprised if it can&#39;t be done, so maybe I&#39;m just not using the best keywords in my Google search...

Any pointers or recommendations?

How can I read command line parameters from an R script?

I am trying to invoke a method via reflection with parameters and I get:

&gt; object does not match target type

If I invoke a method without parameters, it works fine. Based on the following code if I call the method `Test(&quot;TestNoParameters&quot;)`, it works fine. However if I call `Test(&quot;Run&quot;)`, I get an exception. Is something wrong with my code?

My initial purpose was to pass an array of objects e.g. `public void Run(object[] options)` but this did not work and I tried something simpler e.g. string without success.

    // Assembly1.dll
    namespace TestAssembly
    {
        public class Main
        {
            public void Run(string parameters)
            { 
                // Do something... 
            }
            public void TestNoParameters()
            {
                // Do something... 
            }
        }
    }
    
    // Executing Assembly.exe
    public class TestReflection
    {
        public void Test(string methodName)
        {
            Assembly assembly = Assembly.LoadFile(&quot;...Assembly1.dll&quot;);
            Type type = assembly.GetType(&quot;TestAssembly.Main&quot;);

            if (type != null)
            {
                MethodInfo methodInfo = type.GetMethod(methodName);

                if (methodInfo != null)
                {
                    object result = null;
                    ParameterInfo[] parameters = methodInfo.GetParameters();
                    object classInstance = Activator.CreateInstance(type, null);

                    if (parameters.Length == 0)
                    {
                        // This works fine
                        result = methodInfo.Invoke(classInstance, null);
                    }
                    else
                    {
                        object[] parametersArray = new object[] { &quot;Hello&quot; };
    
                        // The invoke does NOT work;
                        // it throws &quot;Object does not match target type&quot;             
                        result = methodInfo.Invoke(methodInfo, parametersArray);
                    }
                }
            }
        }
    }

Reflection: How to Invoke Method with parameters

I have a view like this:

    CREATE VIEW MyView AS
       SELECT Column FROM Table WHERE Value = 2;

I&#39;d like to make it more generic, it means to change 2  into a variable. I tried this:

    CREATE VIEW MyView AS
       SELECT Column FROM Table WHERE Value = @MyVariable;

But MySQL doesn&#39;t allow this.

I found an ugly workaround:

    CREATE FUNCTION GetMyVariable() RETURNS INTEGER DETERMINISTIC NO SQL
    BEGIN RETURN @MyVariable; END|

And then the view is:

    CREATE VIEW MyView AS
       SELECT Column FROM Table WHERE Value = GetMyVariable();

But it looks really crappy, and the usage is also crappy - I have to set the @MyVariable before each usage of the view.

Is there a solution, that I could use like this:

    SELECT Column FROM MyView(2) WHERE (...)

The concrete situation is as follows:
I have a table storing information about the denied request:

    CREATE TABLE Denial
    (
    	Id INTEGER UNSIGNED AUTO_INCREMENT,
    		PRIMARY KEY(Id),
    	DateTime DATETIME NOT NULL,
    	FeatureId MEDIUMINT UNSIGNED NOT NULL,
    		FOREIGN KEY (FeatureId)
    			REFERENCES Feature (Id)
    			ON UPDATE CASCADE ON DELETE RESTRICT,
    	UserHostId MEDIUMINT UNSIGNED NOT NULL,
    		FOREIGN KEY (UserHostId)
    			REFERENCES UserHost (Id)
    			ON UPDATE CASCADE ON DELETE RESTRICT,
    	Multiplicity MEDIUMINT UNSIGNED NOT NULL DEFAULT 1,
    	UNIQUE INDEX DenialIndex (FeatureId, DateTime, UserHostId)
    ) ENGINE = InnoDB;

A multiplicity is a number of identical requests recorded in the same second. I want to display a list of denials, but sometimes, when the application gets denied, it retries a couple times just to make sure. So usually, when the same user gets denial 3 times on the same feature in a couple seconds it is actually one denial. If we&#39;d have one more resource, to fulfill this request, the next two denials would not happen. So we want to group the denials in report allowing the user to specify the timespan in which denials should be grouped. E.g. if we have denials (for user 1 on feature 1) in timestamps: 1,2,24,26,27,45 and user wants to group denials that are closer to each other than 4 sec, he should get something like this: 1 (x2), 24 (x3), 45 (x1). We can assume, that spaces between real denials are much bigger than between duplications. I solved the problem in the following way:

    CREATE FUNCTION GetDenialMergingTime()
    	RETURNS INTEGER UNSIGNED
    	DETERMINISTIC NO SQL
    BEGIN
    	IF ISNULL(@DenialMergingTime) THEN
    		RETURN 0;
    	ELSE
    		RETURN @DenialMergingTime;
    	END IF;
    END|
    
    CREATE VIEW MergedDenialsViewHelper AS
    	SELECT MIN(Second.DateTime) AS GroupTime,
    		First.FeatureId,
    		First.UserHostId,
    		SUM(Second.Multiplicity) AS MultiplicitySum
    	FROM Denial AS First 
    		JOIN Denial AS Second 
    			ON First.FeatureId = Second.FeatureId
    				AND First.UserHostId = Second.UserHostId
    				AND First.DateTime &gt;= Second.DateTime
    				AND First.DateTime - Second.DateTime &lt; GetDenialMergingTime()
    	GROUP BY First.DateTime, First.FeatureId, First.UserHostId, First.Licenses;
    
    CREATE VIEW MergedDenials AS
    	SELECT GroupTime, 
    		FeatureId,
    		UserHostId, 
    		MAX(MultiplicitySum) AS MultiplicitySum
    	FROM MergedDenialsViewHelper
    	GROUP BY GroupTime, FeatureId, UserHostId;

Then to show denials from user 1 and 2 on features 3 and 4 merged every 5 seconds all you have to do is:

    SET @DenialMergingTime := 5;
    SELECT GroupTime, FeatureId, UserHostId, MultiplicitySum FROM MergedDenials WHERE UserHostId IN (1, 2) AND FeatureId IN (3, 4);

I use the view because in it it&#39;s easy to filter data and to use it explicitly in the jQuery grid, automatically order, limit number of records and so on. 

But it&#39;s just an ugly workaround. Is there a proper way to do this?

Content Type	Original Author	Original Content on Stackoverflow
Question	Lilz	View Question on Stackoverflow
Solution 1 - Ruby on-Rails	juanm55	View Answer on Stackoverflow
Solution 2 - Ruby on-Rails	Jonathan Leung	View Answer on Stackoverflow
Solution 3 - Ruby on-Rails	MattMcKnight	View Answer on Stackoverflow
Solution 4 - Ruby on-Rails	bensie	View Answer on Stackoverflow

pass parameter by link_to ruby on rails

Ruby on-Rails Problem Overview

Ruby on-Rails Solutions

Solution 1 - Ruby on-Rails

Solution 2 - Ruby on-Rails

Solution 3 - Ruby on-Rails

Solution 4 - Ruby on-Rails

Why are circular references considered harmful?

How can I "zip sort" parallel numpy arrays?

Attributions