SEARCH KEYWORD -- Class


  var in JavaScript

Geoff published an article sometime ago--"How one missing var ruined our launch". This article described one case where MelonCard uses Node.js as their backend system, suddenly there was a small registration peak period--50-100 people registered concurrently, then the entire website stopped responding and many other strange problems showed up. When they were investigating the source of the problem, they found one missing var in the following code.app.all(‘/apps/:user_id/status’, fun...

   JavaScript,Scope,variable     2012-05-26 12:35:36

  Should we use Abstract class or Interface?

When we write programs, we may often get into a situation where we don't know whether we should use Abstract class or Interface when we want to define an abstract object. These two are very similar and they are interchangeable in many cases. On Stackoverflow, this question is asked lots of times and it's related to many programming languages. Also in the official documentation of PHP regarding the Abstract class and Interface, people are arguing about this. To understand this question, their dif...

   DIFFERENCE,INTERFACE,ABSTRACT CLASS,COMPARISON,OOP     2013-04-15 11:44:36

  QScrollArea Scrollbar Display Solution

Qt framework is a popular C++ GUI framework developed by Nokia. And it is also cross platform compatible. Many developers are using Qt to develop C++ GUI programs. In Qt, some important components are deserved our close attention. Many developers faced the problem when they put some widgets in a QScrollArea widget and they want it to display scroll bars when the widgets inside the QScrollArea overflows. After many experiments, I propose a way which can show scroll bars as you expected. The...

   C++,Qt,GUI,QScrollBar,ScrollBar,Not display,Solution     2012-03-03 07:48:36

  Fix 'this authentication plugin is not supported' issue while using Go to connect MySQL 8

MySQL 8 has changed its default authentication plugin from mysql_native_password to caching_sha2_password to improve its security. However many third party libraries seem act slowly to catch up with this change. This causes some compatible issues with their connection to MySQL. One of the issues is seen in Go libraries while it's trying to connect to MySQL 8. The specific error has been observed is "this authentication plugin is not supported". The root cause of this issue is that the go-sq...

   MYSQL,GO,MYSQL 8,AUTHENTICATION PLUGIN     2018-07-11 08:55:02

  A small trick on using console.log to print data in JavaScript

When debugging JavaScript application, one may frequently use console.log to print data so that it is easy to debug when issue occurs and also helps on understand the data flow. The common way of printing a variable would be something like.  let user = { name: "test" }; console.log(user); In this case it will print: { name: 'test' } This is OK when there is no much logging or the program is not complicated. But it becomes difficult to debug if there are lots of variables to be printed ...

   JAVASCRIPT,CONSOLE.LOG,DEBUGGING     2019-09-03 10:24:24

  Permutation algorithm with JavaScript

In secondary school, we have learned permutation. Basically, for n numbers, the number of permutations for these n numbers can be calculated to n! which is called 'n factorial'. But to display all the permutations on the screen, we need to use a recursive function. The problem is how to write this function.  Next I write a program to display the permutations for n numbers with JavaScript. First, we need to understand that from these n numbers, we can first take any one number from it, and t...

   JavaScript,Permutation,Algorithm,Impleme     2011-09-21 12:02:35

  A Python assignment trap

Python has no assignment, it only has reference. Assume, we have following code snippet: >>> values = [0, 1, 2] >>> values[1] = values >>> values [0, [...], 2] Why the result is not [0, [0, 1, 2], 2], instead it goes into an infinite loop? To understand this, we need to understand some basics about Python. Python has no variables, it only has labels. When we run: values = [0, 1, 2] Python will first create a list object [0,1,2], then it labels it as values. If we later...

   Python,Assignment,Trap,Shallow copy     2013-07-19 22:08:36

  do {...} while (0) in macros

If you are a C programmer, you must be familiar with macros. They are powerful and can help you ease your work if used correctly. However, if you don't define macros carefully, they may bite you and drive you crazy. In many C programs, you may see a special macro definition which may seem not so straightforward. Here is one example: #define __set_task_state(tsk, state_value) \ do { (tsk)->state = (state_value); } while (0) There are many this kind of macros which uses do{...}while(0)...

   C,macro,C++     2014-01-23 07:16:13

  template function in class in C++

We can define template function in a class, but one thing we should pay attention to is that the member function template definition (in addition to the declaration) should be in the header file, not the cpp, though it does not have to be in the body of the class declaration itself.Example //Sorter.h#pragma onceclass Sorter{public:    Sorter(void);    ~Sorter(void);    template <class type> static void qsort(type arr[],int start,int end);};templ...

   C++,template function,class,definition,d     2011-08-07 09:39:56

  Art of code comment

Note : This post is just for fun. Please be careful about these tricks. Code comment is to provide complementary comment to abstract codes. We will introduce two comment styles while we are debugging our codes. we should avoid these styles in production codes. 1. if else style Only execute eatKfc() //* eatKfc(); /*/ eatMcdonalds(); //*/ Only execute eatMcdonalds() /* eatKfc(); /*/ eatMcdonalds(); //*/ Execute both //* eatKfc(); //*/ eatMcdonalds(...

   Comment,Style     2013-08-19 04:19:40

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