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R: preventing unlist to drop NULL values

I'm running into a strange problem. I have a vector of lists and I use unlist on them. Some of the elements in the vectors are NULL and unlist seems to be dropping them. How can I prevent this? Here's a simple (non) working example showing this unwanted feature of unlist a = c(list("p1"=2, "p2"=5), list("p1"=3, "p2"=4), l...

C# 4: how to in-line detect for nulls?

In C# 4, wasn't there a short cut for checking for null values like so: if( myobject?.myproperty?.myotherproperty?.value != null ) The value would return null and not throw an exception. Anyone have a link to how to use it or at least the syntax? ...

django left join with null

The model: class Product(models.Model): name = models.CharField(max_length = 128) def __unicode__(self): return self.name class Receipt(models.Model): name = models.CharField(max_length=128) components = models.ManyToManyField(Product, through='ReceiptComponent') class Admin: pass def __unicode__(self): return ...

Java Constructor Style (Check parameters aren't null)

What are the best practices if you have a class which accepts some parameters but none of them are allowed to be null? The following is obvious but the exception is a little unspecific: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null || two == null) { throw new I...

Compilers behave differently with a null parameter of a generic method

The following code compiles perfectly with Eclipse, but fails to compile with javac: public class HowBizarre { public static <P extends Number, T extends P> void doIt(P value) { } public static void main(String[] args) { doIt(null); } } I simplified the code, so T is not used at all now. Still, I d...

Varchar columns: Nullable or not.

The database development standards in our organization state the varchar fields should not allow null values. They should have a default value of an empty string (""). I know this makes querying and concatenation easier, but today, one of my coworkers questioned me about why that standard only existed for varchar types an not other dat...

Ultrawingrid - how to display #1/1/1800# as blank ( as if null )

Ultrawingrid 9.2 VS2008 .net 3.5 My wingrid uses a bindingsource. All datetimes which are null in SQL Server are delivered to the bindingsource as #1/1/1800# I would like Ultrawingrid to display this date as blank as it would a null from source. Also, if the date is null in the grid ( i.e. blanked out ) I would like to update the dat...

Difference between null==object and object==null

Hi I would like to know diff between the above comparisons? I am getting null pointer exception when I check object.getItems() == null. But if I change it to null == object.getItems(), it workes fine. I did look into this http://stackoverflow.com/questions/2938476/what-is-the-difference-between-null-object-and-objectnull-closed But I d...

jquery getjson works fine in mac, and fails in windows

this code loads the data jQuery.ajax({ type: "GET", url: "getOptionsJson.php", cache: false, dataType: "json", data: "config_id="+config_id, success: function(json) { jQuery.extend(dataArr, json.ajax); jQuery.extend(opts, json.ajax2); printResult(config_id)...

Need help with NSString that returns (null)

Hi, I have an NSString in an NSObject file, I inherited this NSString into my MainViewController where it gets the value. Now, I want to use this NSString value in another UIViewController subclass. From some reason I always get (null) Here's my code: MainViewController: leftWebViewUrl = [NSMutableString stringWithString:leftWebVi...

MVC null model problem

hello, i have created two create actions..one to call the create view and the other to process the create view using httppost. when i call the create view, it gets published correctly , dropdowns and all. the problem is that when i fill out the create form and click on the submit button, i get an error; Object reference not set to an ...

Return Empty String as NULL

I have a listbox select and I want when the user selects null for the empty string it produces to pull the nulls from the SQL table. Here's what I have now. Blank strings return nothing because there are no empty fields in the table. SELECT * FROM dbo.Table WHERE ID = " & TextBox2.Text & " and And Field1 IN (" & Msg1 & ") How do I co...

which is more effective [ if(NULL==variables) or if(variables==NULL) ]

hi expert, want to ask, in java if(NULL==variables) or if(variables==NULL) which will be more effective and what are the difference, thanks ...

mysql showing null values for group by statements

I'm doing: select sum(clicks), date from stats group by date ...however when the sum is null for some date, the whole row is discarded, I want to see: | null | some_date |, how to do so? ...

SQL-Join with NULL-columns

I'm having the following tables: Table a +-------+------------------+------+-----+ | Field | Type | Null | Key | +-------+------------------+------+-----+ | bid | int(10) unsigned | YES | | | cid | int(10) unsigned | YES | | +-------+------------------+------+-----+ Table b +-------+------------------+------+ ...

Would a pointer to a pointer to nil match against NULL?

Example: A validation method contains this check to see if an NSError object shall be created or not: - (BOOL)validateCompanyName:(NSString *)newName error:(NSError **)outError { if (outError != NULL) { // do it... Now I pass an NSError object, like this: NSError *error = nil; BOOL ok = [self validateCompanyName:@"Apple"...

Passing NULL value

Hi. I use an instance of NSXMLParser. I store found chars in NSMutableStrings that are stored in an NSMutableDictionary and these Dicts are then added to an NSMutableArray. When I test this everything seems normal: I count 1 array, x dictionnaries and x strings. In a detailview controller file I want to show my parsed results. I call t...

Android ListView: getTag() returns null

Hallo all, I have a ListView which contains a Button in each line. The following code is part of the getView() Method public View getView(final int position, View convertView, ViewGroup parent) { View row = convertView; TextView tv; Button saveA_button; EditText edittext; FITB_ViewWrapper wrapper...

If/Then in SQL Embedded in VBA

I've got a string like this in my Excel VBA: strSQL = "SELECT * FROM Total WHERE (SimulationID = (" & TextBox1.Text & ") And Test1 = (" & Example & "))" However, sometimes Test will be 'is null', which makes the query And Example = is NULL How can I change it to add an if/then statement or something to make it say And Example is ...

Passing null as a param for replace() in javascript behaving weird?

I have the follwing jQuery: $("#textArea").keyup(function(){ var textAreaValue = $("textArea"); if(!textArea.value.indexOf("some string")){ textArea.value = textArea.value.replace("some string",null); alert("It was there!"); } }); Is it normal for e...