I'm trying to pass a string parameter in MVC3.
The URL that gets generated is:
http://localhost:50164/Property/Browse/Oregon
This appears to be the Property controller class in the function "Browse" with parameter "Oregon".
The right function gets called, but the string appears to be empty.
public ViewResult Browse(string location)
{
//counted_properties: 3 counted_properties_here: 0
ViewData["counted_properties"] = db.Properties.Count(); // debug 3 total
ViewData["counted_properties_here"] = db.Properties.Where(p => p.location == "Oregon").Count(); // debug 1 (the right answer!)
//return View(db.Properties.Where(p => p.location == tmp_location).ToList()); // 0 (bad!)
ViewData["the_location"] = location;
int size = tmp_location.Length; // unhandled null exception when tmp_location = location
ViewData["location_length"] = size;
// return View(db.Properties.Where(p => p.location == "Oregon").ToList()); // Right! but hardcoded
return View(db.Properties.Where(p => p.location == location).ToList());
}
When I return the lambda using the hard coded string (Oregon), I get the right answer.
When I return the lambda using the parameter (string location) I get zero results.
When I try to display ViewData["the_location"] which is a direct copy of the parameter it is blank. Maybe I'm not trying to display it correctly. Here is my view:
Location: #Html.Encode(ViewData["the_location"] )
When I call location.Length I get an unhandled null exception, but this works when I call Length on a hard coded parameter like "Oregon".
It looks like somehow the string is empty, but this doesn't make sense since I see "Oregon" in the URL when it gets to the property/browse function.
I'm beginning to wonder if I am allowed to pass strings as arguments in MVC as I haven't seen any examples with string parameters.
This is a continuation of an unsolved problem:
C#/ASP.NET lambda conversion
By the way, I'm not trying to promote Oregon here. I've never been there. Maybe it's a good place, though.
Check your routing. Traditionally URLs like the one you give will map the value ("Oregon") to the "id" parameter, rather than the location parameter that you're trying to use. Either rename the parameter or change the route to use "{controller}/{action}/{location}".
Related
This class example was taken from here.
class Celsius:
def __init__(self, temperature = 0):
self.temperature = temperature
def to_fahrenheit(self):
return (self.temperature * 1.8) + 32
def get_temperature(self):
print("Getting value")
return self._temperature
def set_temperature(self, value):
if value < -273:
raise ValueError("Temperature below -273 is not possible")
print("Setting value")
self._temperature = value
temperature = property(get_temperature, set_temperature)
The idea here is that when we create an instance of Celsius and set the temperature attribute (e.g. foo = Celsus (-1000) ), we want to make sure that the attribute is not less than -273 BEFORE setting the temperature attribute.
I don't understand how it seems to bypass self.temperature = temperature and go straight to the last line. It seems to me like there are three attributes/properties created here: the Class attribute, temperature; the Instance attribute, temperature; and the set_temperature function which sets the attribute _temperature.
What I DO understand is that the last line (the assignment statement) must run the code property(get_temperature, set_temperature) which runs the functions get_temperature and set_temperature and intern sets the private attribute/property _temperature.
Moreover, if I run: foo = Celsius(100) and then foo.temperature, how is the result of foo.temperature coming from temperature = property(get_temperature, set_temperature) and thus _temperature AND NOT self.temperature = temperature? Why even have self.temperature = temperature if temperature = property(get_temperature, set_temperature) gets ran every time the foo.temperature call is made?
More questions...
Why do we have two attributes with the same name (e.g. temperature) and how does the code know to retrieve the value of _temperature when foo.temperature is called?
Why do we need private attributes/properties an not just temperature?
How does set_temperature(self, value) obtain the attribute for parameter value (e.g. the argument that replaces value)?
In short, please explain this to me like a three year old since I have only been programming a few months. Thank you in advance!
When we are first taught about classes/objects/attributes we are often told something like this:
When you look up an attribute like x.foo it first looks to see if
'foo' is an instance variable and returns it, if not it checks if
'foo' is defined in the class of x and returns that, otherwise an
AttributeError is raised.
This describes what happens most of the time but does not leave room for descriptors. So if you currently think the above is all there is about attribute lookup property and other descriptors will seem like an exception to these rules.
A descriptor basically defines what to do when looking up / setting an attribute of some instance, property is an implementation that lets you define your own functions to call when getting / setting / deleting an attribute.
When you do temperature = property(get_temperature, set_temperature) you are specifying that when x.temperature is retrieved it should call x.get_temperature() and the return value of that call will be what x.temperature evaluates to.
by specifying set_temperature as the setter of the property it states that when ever x.temperature is assigned to something it should call set_temperature with the value assigned as an argument.
I'd recommend you try stepping through your code in pythontutor, it will show you exactly when get_temerature and set_temperature are called after which statements.
I am currently using ReSharper V8.1. I've only recently began using ReSharper and have found some interest in their LiveTemplate Macros. I've conjured up a solution to return a list of HotspotItems from a constant, similar to ReSharper's predefined macro "Comma-delimited list of values". In the method I take the constant variable of the template parameter and do a split string on them to provide a collection of HotSpotItems. Unfortunately it doesn't work if I use the macro more than one time within a template. Below is an extreme hack job showing my implementation of the method HotspotItems of IMacroImplementation.
I am hoping that someone out there may have done some work in this area and could possibly provide an example of how they've implemented IMacroImplementation which provides a list of items from a constant and also allows for multiple uses within a single template.
Thank you.
public override HotspotItems GetLookupItems(IHotspotContext context)
{
HotspotItems hotSpotItems = null;
foreach (var hotspot in context.HotspotSession.Hotspots)
{
if (hotspot.Expression != null && ((MacroCallExpressionNew)hotspot.Expression).Definition is Macros.DisplayMultipleItems)
{
//hotspot.CurrentValue
var multiItems = ((MacroCallExpressionNew) hotspot.Expression).Definition as DisplayMultipleItems;
if (!multiItems.ItemSet)
{
var expression = hotspot.Expression as MacroCallExpressionNew;
IMacroParameterValueNew baseValue = expression.Parameters[0].GetValue(context.SessionContext.Solution.GetLifetime(), context.HotspotSession);
string templateValue = baseValue.GetValue();
multiItems.ItemSet = true;
if (!string.IsNullOrEmpty(templateValue) && templateValue.Split(',').Any())
{
var lookupItems = templateValue.Split(',').Select(param => new TextLookupItem(param)).Cast<ILookupItem>().ToList();
if (hotSpotItems == null)
hotSpotItems = new HotspotItems(lookupItems);
else
{
foreach (var item in lookupItems)
{
hotSpotItems.Items.Add(item);
}
}
}
}
}
}
return hotSpotItems;
}
You should fire up dotPeek and point it to the ReSharper bin directory and take a look at ListMacroDef and ListMacroImpl, which is the implementation for the comma-delimited list macro.
The definition derives from SimpleMacroDefinition. It gets given the parameters in the call to GetPlaceholder, looks at the first and splits it by comma, returning the first item as the placeholder.
ListMacroImpl is just as simple. Its constructor has an [Optional] parameter of type MacroParameterValueCollection. This is the list of parameter values specified in the hotspot editor. You'll want to check for null and take the first parameter, which will be your delimited list. It then overrides GetLookupItems and returns HotspotItems.Empty if the parameter value is null, or parses the value and returns a list of TextLookupItem.
You don't need to look at the session and list of hotspots - that will get you all hotspots in the session, when you're only interested in the current hotspot, and ReSharper will create a new IMacroImplementation for each hotspot and give you those values in your constructor.
I'm trying to replace a function call like (simplified) Utility.GetString(MyEntity.SomePropertyWithRelatedEntity)=="abc" with an expression visitor into something like p => p.SubRelatedEntities.FirstOrDefault(sre => sre.SomeFlag==true).SomePropertyWithRelatedEntity.
It means, the datamodel goes like:
MyEntity -> RelatedEntity -> SubRelatedEntity
I'm trying to return a string value from the SubRelatedEntity, based on some rules in the RelatedEntity, so I don't have to re-write / copy/paste the whole filtering rules in every usage; that's why I put inside a "call-signature", so my expression visitor can identify it and replace the fake-call to Utility.GetString to some complicated lambda expressions.
My expression visitor contains something like:
public override Expression Visit(Expression node)
{
if (node == null)
return null;
Expression result = null;
if (node.NodeType == ExpressionType.Call)
{
MethodCallExpression mce = node as MethodCallExpression;
if (mce.Method.DeclaringType == typeof(Utility) && mce.Method.Name == "GetString")
{
Expression<Func<RelatedEntity, string>> exp = re => re.SubRelatedEntities.FirstOrDefault(sre => sre.SomeFlag == true).SomeStringValue;
result = exp.Body;
}
else
result = base.Visit(node);
}
else
result = base.Visit(node);
return result;
}
Now, the problem is, the "sre" parameter is not bound when called the injected lambda expression. After much research, I see the lambda parameters should be replaced with another expression visitor, specifically searching for the new parameters and replacing them with the old ones. In my situation, however, I don't have an "old parameter" - I have the expression MyEntity.SomePropertyWithRelatedEntity (e.g. an property filled with the related entities) which I need to insert somehow in the generated lambda.
I hope my problem is understandable. Thank you for any insights!
After getting no answers for long time and trying hard to find a solution, I've solved it at the end :o)! It goes like this:
The newly injected lambda expression gets an ParameterExpression - well, this is a 'helper', used when directly calling the lambda, what I don't want (hence, 'parameter not bound' exception when ToEnumerable is called). So, the clue is to make a specialized ExpressionVisitor, which replaces this helper with the original expression, which is of course available in the Arguments[] for the method call, which I try to replace.
Works like a charm, like this you can reuse the same LINQ expressions, something like reusable sub-queries, instead of writing all the same LINQ stuff all time. Notice as well, that expression calling a method is not allowed in EF, in Linq2Sql it worked. Also, all the proposed web articles only replace the parameter instances, when constructing/merging more LINQ expressions together - here, I needed to replace a parameter with an faked-method-call argument, e.g. the method should not be called, it only stands for a code-marker, where I need to put my LINQ sub-query.
Hope this helps somebody, at the end it's pretty simple and logical, when one knows how the expression trees are constructed ;-).
Bye,
Andrej
I am using rich faces select component.
I want dynamic values when user manually type some thing in the select component.
<rich:select enableManualInput="true" defaultLabel="start typing for select" value="#{supplierSearchBean.userInput}">
<a4j:ajax event="keyup" execute="#this" listener="#{supplierSearchBean.userInputChange}"/>
<f:selectItems value="#{supplierSearchBean.selectOptions}" />
</rich:select>
Java code as follows
public void userInputChange(ActionEvent ae){
Map map = ae.getComponent().getAttributes();
System.out.println(map.toString());
}
public void setUserInput(String userInput) {
System.out.println("userINput = " + userInput);
this.userInput = userInput;
}
Here i found 2 issues
1st: setUserINput always print empty string when user type value
2nd: listener method never get call.
any help ?
The problem is most probably that there is no selected value while the user types, and this component restricts the allowed values to the specified select items. A partial input is thus not valid and cannot be bound to your bean.
I think you could get the expected behavior if you use a rich:autocomplete instead. However, if you want to restrict the allowed values, maybe you can keep your rich:select and listen for the selectitem event.
Override getItems function in richfaces-utils.js file in richfaces-core-impl-4.0.0.Final.jar under richfaces-core-impl-4.0.0.Final\META-INF\resources folder.
Change the condition of pushing items to be
if(p != -1)
instead of
if(p == 0)
This should fix the issue.
I'm implementing a search box using CodeIgniter, but I'm not sure about how I should pass the search parameters through. I have three parameters: the search string; product category; and the sort order. They're all optional. Currently, I'm sending the parameters through $_POST to a temporary method, which forwards the parameters to the regular URI form. This works fine. I'm using a weird URI format though:
http://site.com/products/search=computer,sort=price,cat=laptop
Does anyone have a better/cleaner format of passing stuff through?
I was thinking of passing it into the products method as arguments, but since the parameters are optional things would get messy. Should I suck it up, and just turn $_GET methods on? Thanks in advance!
Query Strings
You can enable query strings in CodeIgniter to allow a more standard search function.
Config.php
$config['enable_query_strings'] = FALSE;
Once enabled, you can accept the following in your app:
http://site.com/products/search?term=computer&sort=price&cat=laptop
The benefit here is that the user will find it easy to edit the URL to make a quick change to their search, and your search uses common search functionality.
The down side of this approach is that you are going against one of the design decisions of the CodeIgniter development team. However, my personal opinion is that this is OK provided that query strings are not used for the bulk of your content, only for special cases such as search queries.
A much better approach, and the method the CI developers intended, is to add all your search parameters to the URI instead of a query string like so:
http://site.com/products/search/term/computer/sort/price/cat/laptop
You would then parse all the URI segments from the 3rd segment ("term") forward into an array of key => value pairs with the uri_to_assoc($segment) function from the URI Class.
Class Products extends Controller {
...
// From your code I assume you are calling a search method.
function search()
{
// Get search parameters from URI.
// URI Class is initialized by the system automatically.
$data->search_params = $this->uri->uri_to_assoc(3);
...
}
...
}
This would give you easy access to all the search parameters and they could be in any order in the URI, just like a traditional query string.
$data->search_params would now contain an array of your URI segments:
Array
(
[term] => computer
[sort] => price
[cat] => laptop
)
Read more about the URI Class here: http://codeigniter.com/user_guide/libraries/uri.html
If you're using a fixed number of parameters, you can assign a default value to them and send it instead of not sending the parameter at all. For instance
http://site.com/products/search/all/somevalue/all
Next, in the controller you can ignore the parameter if (parameter == 'all'.)
Class Products extends Controller {
...
// From your code I assume that this your structure.
function index ($search = 'all', $sort = 'price', $cat = 'all')
{
if ('all' == $search)
{
// don't use this parameter
}
// or
if ('all' != $cat)
{
// use this parameter
}
...
}
...
}