Best practice of AngularJs to check if indefinite and null

I would like to know which way to check if a variable is nullor undefined in AngularJSis the best way. First way : if(!myVar){...} Second way : if(myVar === null || myVar === undefined){...} Third way : if(angular.isUndefined(myVar) || myVar === null

getActionBar returning null

This question already has an answer here: getActionBar() returns Null (AppCompat-v7 21) 4 answers I have a activity and I have added setSupportActionBar(toolbar); And I want to display home button on action bar. Home button is from android predefined

Oracle NVL with empty string

I have this table where NULL is the NULL value, not the string NULL: MYCOL -------- NULL example Why does this query not return the NULL row? select * from example_so where nvl(mycol, '') = ''; '' is again NULL in Oracle, because Oracle doesn't suppo

Clarification of the Javascript list

var list = {}; list[19] = 'kapooya'; list[20] = 'apples'; delete list[19]; Does list[19] == 'apples' or null?Apart from the syntax error you get when using varbefore list[19] = 'kapooya', list[19] is undefined after the delete, not null. Technically

Validate if the foreign key exists if it is not null

I have a many-to-one relationship defined in Rails 4: class Event < ActiveRecord::Base belongs_to :user end How do I check, that the :user key exists if it is set? The following correctly checks, that the key exists but does not allow for `nil? value

Null value after the constructor

class test { public static myclass x; test() { try { x=new myclass(); //x is not null here } catch(Exception e) {/*stuff*/} //not null here } //x is null here in any other member method } Please explain a reason for this behavior? Isn't a constructor

json returns null after POST

a.php $(document).ready(function() { $("#submit_form").on("click",function(){ var json_hist = <?php echo $json_history; ?>; $.ajax({ type: "POST", url: "b.php", data: "hist_json="+JSON.stringify(json

what is the real meaning of 'void' in C #?

This question already has an answer here: What is System.Void? 4 answers What is void** in C#? 5 answers I was looking at definition for void type in C#. It's an empty structure that represents a no value. But, what is exactly the difference between

How to get my current location in Google Maps API V2

I'm creating an app where the user needs to see his/her geo location with getMyLocation(), but this is returning null. Is there any solution for this, because I did read that the getMyLocation() method is always returning null. I'm new to Google Maps

Checking null XML data with JavaScript

I get data from XML. I need to check data and if data is null I must hide this. How can I check? <script> downloadUrl("gxml.php", function(data) { var xml = data.responseXML; var markers = xml.documentElement.getElementsByTagName("mar

SQL: @somevalue = null does not work properly

I tried @somevalue = null and it worked that time. But now its not working. How to check if the value is null? In brief what I need to do is if @existPerson is equal to null then INSERT the values into the database. But if it exists then return -2. I

Rails says the class is zero despite the console database

I have a database of objects (tools) in my Ruby on Rails project. When I use "rails dbconsole" and select * from tools; it returns a whole list of tool objects. But when I try to view the following page, it gives me an error. Page: <!DOCTYPE

Can there be a C ++ type that takes 0 bytes

I'm trying to declare a C++ variable that takes up zero bytes. Its in a union, and I started with the type as int[0]. I don't know if that is actually zero bytes (although sizeof(int[0]) was 0). I need a better way to declare a 0 byte type, and hopef

Check if the table is null or not in php

I have an array like below which is generated by parsing a xml url. The array is Array ( [Tags] => SimpleXMLElement Object ( [0] => ) ) The array name is $result. Now I want to check that if the array received like above I want to print a message of

StringBuffer behavior for NULL objects

I am not able to understand the following behavior of StringBuilder when NULL objects are appended to an instance: public class StringBufferTest { /** * @param args */ public static void main(String[] args) { String nullOb = null; StringBuilder lsb =

PHP and returning null references (revisited)

I've asked a question before, that essentially took the $null = null approach as a given, to returning a null reference in PHP. After some cursory Googling, I didn't turn up much; leaving me to assume that the aforementioned approach is the best (rea

PostgreSQL: order by sum of calculated values

I have a table tips that is defined as follows: CREATE TABLE tips ( tip_id bigserial NOT NULL, tip text NOT NULL, author text NOT NULL, post_date bigint NOT NULL, likers character varying(16)[], dislikers character varying(16)[], likes integer NOT NU

Manage DBNull and null in ASP.NET

What is the best way of rewriting these (erroneous) lines? bool? result = dr["result"] == DBNull.Value ? null : Convert.ToInt32(dr["result"]); ...and... dr["result"] = result ?? DBNull.Value; Both do not compile. I am using t

Why is my element nil?

Why when I do an alert of the value (see below) it returns null? When an element with that ID exists? // make reference to divs var countdown_timer = document.getElementById("countdown_timer"); var countdown_image = document.getElementById("

objectForKey stringValue crashes my application?

I have a class that I use to setup objects in an array. In this class I have a custom "initWithDictionary", where I parse a JSON dictionary. However, as I am running into NSNull, this crashes my app. To get around this, I set up a class that han

Why is there a null value in JavaScript?

In JavaScript, there are two values which basically say 'I don't exist' - undefined and null. A property to which a programmer has not assigned anything will be undefined, but in order for a property to become null, null must be explicitly assigned t

Why nowhere?

I saw this piece of code somewhere and wondered: when and why would somebody do the following: doSomething( (MyClass) null ); Have you ever done this? Could you please share your experience?If doSomething is overloaded, you need to cast the null expl