self.object = nil calls your setter, which will release the old value, set the member to nil, and possibly do other things (it’s a method, so it could do anything). The “anything” part of that is potentially dangerous; see this question, for example. [object release] releases the old value, but leaves the member as a … Read more
There are three types which it might be valid to use the array derefence syntax on: Arrays Strings (to access the character at the given position) Object (objects implementing the ArrayAccess interface) For all other types, PHP just returns the undefined variable. Array dereference is handled by the FETCH_DIM_R opcode, which uses zend_fetch_dimension_address_read() to fetch … Read more
I’m no expert at SQL, but why not just sort by if something is null first then sort by how you wanted to sort it. Photo.order(‘collection_id IS NULL, collection_id DESC’) # Null’s last Photo.order(‘collection_id IS NOT NULL, collection_id DESC’) # Null’s first If you are only using PostgreSQL, you can also do this Photo.order(‘collection_id DESC … Read more
The C standard does not require null pointers to be at the machine’s address zero. HOWEVER, casting a 0 constant to a pointer value must result in a NULL pointer (ยง6.3.2.3/3), and evaluating the null pointer as a boolean must be false. This can be a bit awkward if you really do want a zero … Read more
I agree with Maravilho Singa’s answer. It appears to be a bug in gradle. I found another solution here: removing the .gradle directory in the root project directory will fix the problem.
Check the jQuery FAQ… You can use the length property of the jQuery collection returned by your selector: if ( $(‘#myDiv’).length ){}
Directly from Apple: The NSNull class defines a singleton object you use to represent null values in situations where nil is prohibited as a value (typically in a collection object such as an array or a dictionary). So in your example, that’s exactly what’s happening, the programmer is choosing to put a null object into … Read more
Aside from what you’d like the precedence to be, what it is according to ECMA, what it is according to the MS spec and what csc actually does, I have one bit of advice: Don’t do this. I think it’s much clearer to write: string c = (a ?? “”) + (b ?? “”); Alternatively, … Read more
This to me sounds like a reasonably common problem that junior to intermediate developers tend to face at some point: they either don’t know or don’t trust the contracts they are participating in and defensively overcheck for nulls. Additionally, when writing their own code, they tend to rely on returning nulls to indicate something thus … Read more
No, MySQL is doing the right thing, according to the SQL-99 specification. https://mariadb.com/kb/en/sql-99/constraint_type-unique-constraint/ A UNIQUE Constraint makes it impossible to COMMIT any operation that would cause the unique key to contain any non-null duplicate values. (Multiple null values are allowed, since the null value is never equal to anything, even another null value.) If you … Read more