Assumed I defined my dict as below.
Dictionary<list<int>, list<string>> d = new Dictionary<List<int>, list<string>>()
How can I retrieve the dict key and value rapidly.
[update]
I want to get the Key - List content.
I tried a simple way as below
List<int> KeysList= new List<int>(d.Keys);
But it doesn't work at the complex key on my case.
Can I only use the KeyValuePair as below?
foreach (KeyValuePair<List<int>, List<string>> pair in d)
{
KeysList= new List<int>(pair.Key);
}
You've got a potential problem there to start with: List<T> doesn't override Equals, so you'd have to use the exact same key reference to fetch the value for a key.
Having said that, if you have that reference, it's as simple as
List<string> value = d[key];
or
List<string> value;
if (d.TryGetValue(key, out value))
{
...
}
It's pretty unusual to have a List<T> as a key though - can you tell us more about what you're trying to do? There may be a better approach.
Related
maybe another one stumbled upon this topic and found a nice solution. Using the HATEOAS REST approach with help of Spring HATEOAS project works pretty well for link building to resources. But in the end, to map flattened resources back to an entity object tree, I need to disassemble my link and query the persistence backend. Example given, I have an entity Item, referencing ItemType (Many-to-one). Natural key of item is the composite of ItemType foreign key and Item code itself. The URL I map in ItemController using the link builder is
#RequestMapping("/catalog/items/{itemTypeCode}_{itemCode}")
Now a unique link for an item is e.g. http://www.sample.com/catalog/items/p_abc123
To invert this link I do some very ugly string work:
#Override
public Item fromLink(Link link) {
Assert.notNull(link);
String baseLink = linkTo(ColorTypeController.class).toString() + "/";
String itemTypeAndItemPart = link.getHref().replace(baseLink, "");
int indexOfSplit = itemTypeAndItemPart.indexOf('_');
ItemType itemType = new ItemType();
itemType.setCode(itemTypeAndItemPart.substring(0, indexOfSplit));
Item item = new Item();
item.setItemType(itemType);
item.setCode(itemTypeAndItemPart.substring(indexOfSplit + 1));
return item;
}
And all the time I am wondering, If there isn't a much nicer and more flexible approach (beware of any query string part, that will break the code) to do this inverse mapping. I actually do not want to call another MVC controller from within a controller but it would be nice, to somehow utilize the dispatcher servlet disassembly functions to deconstruct the URL into something more handy to work with. Any helpful hints for me? Thx alot :)
You can use a UriTemplate. Its match method returns a map of variables and their values that have been extracted from the URI. For example:
UriTemplate uriTemplate = new UriTemplate("/catalog/items/{itemTypeCode}_{itemCode}");
Map<String, String> variables = uriTemplate.match("http://www.sample.com/catalog/items/p_abc123");
String itemTypeCode = variables.get("itemTypeCode"); // "p"
String itemCode = variables.get("itemCode"); // "abc123"
i am getting error "Object reference not set to an instance of an object." my is here,
public class UserProfession
{
public UserProfession()
{
}
public System.String[] Designation
{
get;
set;
}
}
then i am using it like,
UserProfession.Designation[0] =txt_Search.Text.ToString();
Error i mentioned you hopes for your suggestions .
-Thanks
When you make an assignment to an array property, like this:
UserProfession.Designation[0] =txt_Search.Text.ToString();
what you are actually doing is calling the get section for that property... not the set. This returns the object supported the property... the whole object, and not just the index. Index lookup does not happen until after the object is returned. Once you have that object, accessing an index works in the normal way.
You get this specific exception because you have the expression UserProfession.Designation that should return a reference to an array object, but because you never initialize the array there is nothing there when you then try to find reference the 0th element. At this point the framework discovers that the array (your "object reference") is "not set to an instance of an object"... which is just a fancy way of saying it's null.
In other words, you need to have an already existing array to hold the value you want to assign. That means doing something like this:
Designation = new String[10];
public String[] Designation
{
get;
set;
}
However, notice that we never used the set section? So you can simplify that further, like this:
Designation = new String[10];
public String[] Designation {get;private set;}
This will keep client code from completely swapping an entire array out from under your object, but otherwise will provide the full functionality of an array property. If you provide your own backing store for the array, you could even get rid of the setter entirely with no loss of functionality:
private string[] _designation = new string[10];
public string[] Designation {get {return _designation;} }
But let's add one more wrinkle: your desire to assign the to array before initializing it indicates to me that you likely don't really know how big it will be up front. If that's the case, you probably want a collection of some kind instead of an array. A generic List is a convenient and very compatible replacement for an array. That would look like this:
private List<string> _designation = new List<string>();
public List<string> Designation {get {return _designation;}}
You can still access items in that list by index, just like you would with an array. The only difference you need to worry about right now is how you add new items:
UserProfession.Designation.Add(txt_Search.Text);
Also notice that I removed the .ToString() call. Since your .Text property is almost certainly already a string, calling the .ToString() method is just silly.
You will have to initialize the object, before assigning the value. The initialization should be done just once. I have initialized the array size to ten. You can have your own values here. If you want to resize dynamically, you can use ArrayList
int length = 10;
UserProfession.Designation = new System.String[length];
UserProfession.Designation[0] =txt_Search.Text.ToString();
For more information: http://msdn.microsoft.com/en-us/library/aa287601(v=vs.71).aspx
it must initialize the value before we use because, currently, it is null.
you better add the initialization code in the constructor function.
Using Breeze, what is the simplest way to populate a GUID key when an entity is created?
I'll assume that your entity is configured such that the client is responsible for setting the Guid key for new entities. That's the default for the Guid key of an Entity Framework Code First entity; it is as if the key property were adorned with [DatabaseGenerated(DatabaseGeneratedOption.None)]
The obvious approach is to set the key after creating the entity and before adding it to the manager, e.g.:
function createFoo() {
var foo = fooType.createEntity();
foo.id(breeze.core.getUuid()); // Knockout implementation
manager.addEntity(foo);
}
This may be all you ever need.
On the other hand, you may find that you're creating new Foos in many places and for some strange reason you can't use the createFoo function. You certainly don't want to repeat that code.
You can extend the Foo entity type with id-setting behavior after which you'd be able to write:
function createFoo() {
var foo = fooType.createEntity(); // foo.id is set for you
manager.addEntity(foo);
}
There are two approaches to consider - custom constructor and type initializer; both are described in "Extending Entities"
Constructor
You can initialize the key inside a custom constructor. Breeze calls the constructor both when you create the entity and when it materializes a queried entity. Breeze will replace the initial key value when materializing.
Here's an example that assumes the Knockout model library.
function Foo() {
foo.id(breeze.core.getUuid()); // using KO
}
// one way to get the MetadataStore
var store = manager.metadataStore;
// register the ctor with the Foo type
store.registerEntityTypeCtor("Foo", Foo);
Pretty simple. The only downside is that Breeze will generate a Guid every time it makes an entity, whether creating a new one or materializing one from a query. It's wasted effort during materialization but so what? Well, I suppose that might become a performance issue although I wouldn't assume so until I had measured it.
Initializer
Suppose you measured and the repeated Guid generation is a serious problem (really?). You could set the key in a type initializer instead and only call the Guid generator when creating a new entity.
Breeze calls a type initializer after the entity has been created or materialized from query just before returning that entity to the application. Clearly you don't want to overwrite a materialized key from the database so you'll test the key value to make sure it's not real (i.e. to make sure you're fixing a created entity) before assigning it. Here's an example.
function fooInitializer(foo) {
var emptyGuid = "00000000-0000-0000-0000-000000000000";
if (foo.id() !=== emptyGuid) {
foo.id(breeze.core.getUuid());
}
}
var store = manager.metadataStore;
// register the initializer; no ctor in this example
store.registerEntityTypeCtor("Foo", function(){}, fooInitializer);
Assuming you have a Guid surrogate Key on all your entities like we have in our case, you could code a createInstance factory that does the following in a very generic approach:
function createInstance(breezeEntityManager, typeName) {
var keyProperty = breezeEntityManager.metadataStore.getEntityType(typeName, false).dataProperties.filter(function (p) {
return p.isPartOfKey;
})[0];
var config = {};
config[keyProperty.name] = breeze.core.getUuid();
return breezeEntityManager.createEntity(typeName, config);
}
This way, you won't have to create an initializer for all your entities.
I have the following dictionary in flex, and i d like to sort it by value. Couldn't find any resource.
'1'=>2, '0' =>1, '3'=>4 ..
Any ideas ? How can i sort this by value ?
I searched around for a similar solution, except that I needed to sort the dictionary map and return a sorted collection relating key value pairs. After failing to find a published solution I put together the approach below. This method takes a dictionary as input, creates an array maintaining the association then sorts the resultant array using array.sortOn() and returns the sorted results back as an array. "key" and "value" fields in the array in the example below are used for clarity, but any field name could be used.
This example assumes a string object as a key and a numeric object as a value, though of course any object type could be used, and field parameters adjusted.
The approach below could also be used for sorting by key instead of value by using "key" as the sort field for the sortOn method, and you could use different sort options than the descending numeric sort I used here( AS3 SortOn() documentation) Code below is intentionally non-generic to simplify it for example purposes.
public static function sortDictionaryByValue(d:Dictionary):Array
{
var a:Array = new Array();
for (var dictionaryKey:Object in d)
{
a.push({key:dictionaryKey,value:d[dictionaryKey]});
}
a.sortOn("value",[Array.NUMERIC|Array.DESCENDING]);
return a;
}
Probably not the best way to do it but it works:
var a:Array = new Array();
for each (var v:Number in dict)
{
a.push(v);
}
a.sort();
Does anyone have any recommendations for working with name/value pairs in Flex?
Context:
I want to create a Flex UI for updating a database table. I want the UI to contain the field name(read only) and current field value (which will be editable). Im using the WebService component to retrieve the field value and then asssigning it to an object with the field name hardcoded e.g.
private function resultHandler(event:ResultEvent):Object
{
var resultsObj:Object;
resultsObj = {
name:event.result.name as String,
This approach however is adding the dependency that the table structure/field names will never change. Using the object type also requries that i write my own algorithm to sort the output.
I'm not sure I understand the issue.
If you want to avoid dependency of the properties returned from the event at this point, simply use the event.result object, which is already an associative array.
As for sorting, we would need more context on what you are attempting to sort.
That's pretty simple. Don't use for each in loop. Use For-In Loop
Demo is shown below.
var dicEntry:Object = new Object();
dicEntry["Name"] = "Raj";
dicEntry["sal"] = 10000;
dicEntry["age"] = 33;
for(var key:Object in dicEntry)
{
trace("Object Key: "+key+" Object Value: +dicEntry[key]);
}
That's it.