Silverlight is case sensitive for query string parameters so the following code would return false with "callid=5"
string callId;
if (System.Windows.Browser.HtmlPage.Document.QueryString.TryGetValue("callId", out callId))
{
....
}
Microsoft defends the decision by citing the www.w3.org spec, but I think it leads to a less friendly experience for people trying to link to you, or give a URL over the phone.
Looks like Stackoverflow is case insensitive:
https://stackoverflow.com/search?q=silverlight+bug
https://stackoverflow.com/search?Q=silverlight+bug
I think you should focus on your naming conventions rather than the implementations of standards, making sure to avoid similar field names and mixed case. For example, you can use a convention of words that over the phone can be read out stating "all lowercase" or "all uppercase".
I did this. Don't know if it helps.
var keyName = "";
if (!string.IsNullOrEmpty(keyName = someDictionary.SomeKeys.FirstOrDefault(k => k.ToLowerInvariant() == "size")))
{
var someValue = someDictionary[keyName];
}
Yes, I'm used to it being case sensitive, and therefore have been programming to it for a long time. I know of some people that have implemented methods to do intermediate parsing to convert them all to lowercase, or other things server side, and it really depends on what you are working with specifically.
As for usability, yes it is harder to read. BUT, at the same time a URL over the phone that has a querystring is not easy to give out anyway.
This workaround will not use the power of dictionaries because it will iterate through all keys, but it is likely to be a sufficient work-around for most scenarios.
var keyName = HtmlPage.Document.QueryString.Keys.SingleOrDefault(key => key.Equals("callid", StringComparison.OrdinalIgnoreCase));
string callid;
HtmlPage.Document.QueryString.TryGetValue(keyName, out callid)
You could also transform the whole QueryString dictionary to a new dictionary with a case insensitive comparer if you are having many dictionary lookups.
var insensitiveQueryString = HtmlPage.Document.QueryString.ToDictionary(pair => pair.Key, pair => pair.Value, StringComparer.OrdinalIgnoreCase);
Related
I am used to being able to perform a binary search of a sorted list of, say, Strings or Integers, with code along the lines of:
Vector<String> vstr = new Vector<String>();
// etc...
int index = Collections.binarySearch (vstr, "abcd");
I'm not clear on how codenameone handles standard java methods and classes, but it looks like this could be fixed easily if classes like Integer and String (or the codenameone versions of these) implemented the Comparable interface.
Edit: I now see that code along the lines of the following will do the job.
int index = Collections.binarySearch(vstr, "abcd", new Comparator<String>() {
#Override
public int compare(String object1, String object2) {
return object1.compareTo(object2);
}
});
Adding the Comparable interface (to the various primitive "wrappers") would also would also make it easier to use Collections.sort (another very useful method :-))
You can also sort with a comparator but I agree, this is one of the important enhancements we need to provide in the native VM's on the various platforms personally this is my biggest peeve in our current VM.
Can you file an RFE on that and mention it as a comment in the Number issue?
If we are doing that change might as well do both.
I have a document containing settings for a program like so
setting1;value1;
setting2;value2;
setting3;value3;
I want to loop through these lines, assigning value1 from setting1 to a string named the same (setting1). So that the strings value will be value1.. Hope you get me ?
How can i do this?
Thanks!
Most sensible way is to store therm in a Dictionary:
// untested
Dictionary<string,string> settings =
File.Readlines("filename")
.Select(line => line.Split(";"))
.ToDictionary(parts => parts[0], parts => parts[1]);
// usage:
string value1 = settings["setting1"];
If you really want to assign them all to named fields or properties (but not: variables) in one go then you will need Reflection.
Are you reading in a lot of these? If there are only a couple, variables might work but if there are a lot, a dictionary or similar might be a good choice. http://msdn.microsoft.com/en-us/library/xfhwa508%28v=vs.110%29.aspx or http://www.dotnetperls.com/dictionary
You would just need to change your loop to add a new dictionary entry instead - use the 'setting' as the key and the value as the value.
In Google App Engine, I make lists of referenced properties much like this:
class Referenced(BaseModel):
name = db.StringProperty()
class Thing(BaseModel):
foo_keys = db.ListProperty(db.Key)
def __getattr__(self, attrname):
if attrname == 'foos':
return Referenced.get(self.foo_keys)
else:
return BaseModel.__getattr__(self, attrname)
This way, someone can have a Thing and say thing.foos and get something legitimate out of it. The problem comes when somebody says thing.foos.append(x). This will not save the added property because the underlying list of keys remains unchanged. So I quickly wrote this solution to make it easy to append keys to a list:
class KeyBackedList(list):
def __init__(self, key_class, key_list):
list.__init__(self, key_class.get(key_list))
self.key_class = key_class
self.key_list = key_list
def append(self, value):
self.key_list.append(value.key())
list.append(self, value)
class Thing(BaseModel):
foo_keys = db.ListProperty(db.Key)
def __getattr__(self, attrname):
if attrname == 'foos':
return KeyBackedList(Thing, self.foo_keys)
else:
return BaseModel.__getattr__(self, attrname)
This is great for proof-of-concept, in that it works exactly as expected when calling append. However, I would never give this to other people, since they might mutate the list in other ways (thing[1:9] = whatevs or thing.sort()). Sure, I could go define all the __setslice__ and whatnot, but that seems to leave me open for obnoxious bugs. However, that is the best solution I can come up with.
Is there a better way to do what I am trying to do (something in the Python library perhaps)? Or am I going about this the wrong way and trying to make things too smooth?
If you want to modify things like this, you shouldn't be changing __getattr__ on the model; instead, you should write a custom Property class.
As you've observed, though, creating a workable 'ReferenceListProperty' is difficult and involved, and there are many subtle edge cases. I would recommend sticking with the list of keys, and fetching the referenced entities in your code when needed.
I've got this code (Java, GAE):
// Much earlier:
playerKey = KeyFactory.keyToString(somePlayer.key);
// Then, later...
PersistenceManager pm = assassin.PMF.get().getPersistenceManager();
Key targetKey = KeyFactory.stringToKey(playerKey);
Query query = pm.newQuery(Player.class);
query.setFilter("__key__ == keyParam");
query.declareParameters("com.google.appengine.api.datastore.Key keyParam");
List<Player> players = (List<Player>) query.execute(targetKey); // <-- line 200
which generates this error:
javax.jdo.JDOFatalUserException: Unexpected expression type while parsing query. Are you certain that a field named __key__ exists on your object?
at org.datanucleus.jdo.NucleusJDOHelper.getJDOExceptionForNucleusException(NucleusJDOHelper.java:354)
at org.datanucleus.jdo.JDOQuery.execute(JDOQuery.java:252)
at myapp.Player.validPlayerWithKey(Player.java:200)
// [etc., snip]
But I'm not sure what it wants. I'm trying to search on the JDO id field, which I I thought I read had the special name __key__, in the documentation.
I've tried it with both
query.setFilter("__key__ == keyParam");
and
query.setFilter("ID == keyParam");
with the same results. So, what am I doing wrong? Or, more importantly, how do I do it correctly?
Thanks!
Edit: For completeness's sake, here is the final, working code (based on Gordon's answer, which I have accepted as correct):
Player result = null;
if (playerKey == null)
{
log.log(Level.WARNING, "Tried to find player with null key.");
}
else
{
PersistenceManager pm = assassin.PMF.get().getPersistenceManager();
try {
result = (Player) pm.getObjectById(Player.class, playerKey);
} catch (javax.jdo.JDOObjectNotFoundException notFound) {
// Player not found; we will return null.
result = null;
}
pm.close();
}
return result;
If your objective is to get an object by key, then you should use the PersistenceManager's getObjectByID() method. More details here.
As an aside, trying to construct a query to get something by it's key is something you shouldn't need to do. Although this is how you would work with an SQL database, the Google Data Store does things differently, and this is one of those cases where rather than go through the trouble of constructing a query, Google App Engine lets you get what you want directly. After all, you should only have one entity in the database with a particular key, so there's nothing in the rest of the machinery of a GQL query that you need in this case, hence it can all be skipped for efficiency.
I would recommend you to use the JPA ( http://code.google.com/appengine/docs/java/datastore/usingjpa.html ) to access your data in GAE, it has the very important advantage that you can use the widely known and documented JPA standard (and its JPAQL querying language) to do this kind of things, in portable way (if you stick to the JPA standard, your code will work for GAE, for Hibernate or with EclipseLink without modification)
On this question I solved the problem of querying Google Datastore to retrieve stuff by user (com.google.appengine.api.users.User) like this:
User user = userService.getCurrentUser();
String select_query = "select from " + Greeting.class.getName();
Query query = pm.newQuery(select_query);
query.setFilter("author == paramAuthor");
query.declareParameters("java.lang.String paramAuthor");
greetings = (List<Greeting>) query.execute(user);
The above works fine - but after a bit of messing around I realized this syntax in not very practical as the need to build more complicated queries arises - so I decided to manually build my filters and now I got for example something like the following (where the filter is usually passed in as a string variable but now is built inline for simplicity):
User user = userService.getCurrentUser();
String select_query = "select from " + Greeting.class.getName();
Query query = pm.newQuery(select_query);
query.setFilter("author == '"+ user.getEmail() +"'");
greetings = (List<Greeting>) query.execute();
Obviously this won't work even if this syntax with field = 'value' is supported by JDOQL and it works fine on other fields (String types and Enums). The other strange thing is that looking at the Data viewer in the app-engine dashboard the 'author' field is stored as type User but the value is 'user#gmail.com', and then again when I set it up as parameter (the case above that works fine) I am declaring the parameter as a String then passing down an instance of User (user) which gets serialized with a simple toString() (I guess).
Anyone any idea?
Using string substitution in query languages is always a bad idea. It's far too easy for a user to break out and mess with your environment, and it introduces a whole collection of encoding issues, etc.
What was wrong with your earlier parameter substitution approach? As far as I'm aware, it supports everything, and it sidesteps any parsing issues. As far as the problem with knowing how many arguments to pass goes, you can use Query.executeWithMap or Query.executeWithArray to execute a query with an unknown number of arguments.