You can; the null pointer is implicitly converted into boolean false while non-null pointers are converted into true. From the C++11 standard, section on Boolean Conversions: A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null … Read more
Origin null is the local file system, so that suggests that you’re loading the HTML page that does the load call via a file:/// URL (e.g., just double-clicking it in a local file browser or similar). Most browsers apply the Same Origin Policy to local files by disallowing even loading files from the same directory … Read more
Here’s Stroustrup’s take on this: C++ Style and Technique FAQ In C++, the definition of NULL is 0, so there is only an aesthetic difference. I prefer to avoid macros, so I use 0. Another problem with NULL is that people sometimes mistakenly believe that it is different from 0 and/or not an integer. In … Read more
The compiler is pointing the error to you, you’re comparing a structure instance and nil. They’re not of the same type so it considers it as an invalid comparison and yells at you. What you want to do here is to compare a pointer to your config instance to nil, which is a valid comparison. … Read more
commit schedules the transaction, i.e. it doesn’t happen straightaway but is scheduled as work on the main thread the next time the main thread is ready. I’d suggest adding an onAttach(Activity activity) method to your Fragment and putting a break point on it and seeing when it is called relative to your call to asd(). … Read more
You can either use the “?” operator for a nullable type. public Color? myColor = null; Or use the standard practice for enums that cannot be null by having the FIRST value in the enum (aka 0) be the default value. For example in a case of color None. public Color myColor = Color.None;
convert the NULL values with empty string by wrapping it in COALESCE SELECT CONCAT(COALESCE(`affiliate_name`,”),’-‘,COALESCE(`model`,”),’-‘,COALESCE(`ip`,”),’-‘,COALESCE(`os_type`,”),’-‘,COALESCE(`os_version`,”)) AS device_name FROM devices
What you’re looking for is: if($variable === NULL) {…} Note the ===. When use ==, as you did, PHP treats NULL, false, 0, the empty string, and empty arrays as equal.
I think the succinct summary of why null is undesirable is that meaningless states should not be representable. Suppose I’m modeling a door. It can be in one of three states: open, shut but unlocked, and shut and locked. Now I could model it along the lines of class Door private bool isShut private bool … Read more
There are basically 4 techniques for this task, all of them standard SQL. NOT EXISTS Often fastest in Postgres. SELECT ip FROM login_log l WHERE NOT EXISTS ( SELECT — SELECT list mostly irrelevant; can just be empty in Postgres FROM ip_location WHERE ip = l.ip ); Also consider: What is easier to read in … Read more