A null QString is an uninitialized QString while an empty QString is a QString initialized with an empty string(reference). QString s1; QString s2(“”); if(s1==s2) qDebug()<<“same”;//same else qDebug()<<“not same”; qDebug()<<s1.isNull();//true qDebug()<<s1.isEmpty();//true […]
WordPress image attachment is a little complicated thing. In a post that is inserted an image attachment, you can edit some attributes like alt text, height, width of the inserted […]
I miss the old days when <img> has only a few simple attributes and you only need to know that src is used to store the url of the image. […]
We usually use the following function to bind an event handler to a jQuery object on some event: $( “button” ).on(“click”, function(event){}); The .on method actually has another form: $( […]
QTexStream::readLine() function is a convenient function that can read a line from a file at a time. However, you must pay attention to so called new line. You may find […]
In this post, I talked about the best practice to use forward declaration or include file for a class: only include header files for base class and value member class […]
I used to putting all my code in one .cpp file. That is my style. Don’t be fooled by the “principles” and “theories” advocated by software engineering experts. Those “principles” […]
We know an ordinary member function can not be defined multiple times. Suppose you have the following 3 files a.h, a.cpp, and main.cpp: //a.h #ifndef A_H #define A_H #include <iostream> […]
Today, I ran a program that connects to a database, then a window popped up: Meanwhile, the following error appeared on the console: QSqlDatabase: QMYSQL driver not loaded QSqlDatabase: available […]
You may wonder why the qmake CONFIG variable has values that you never set. Sometimes, you even need to remove some values from CONFIG in your .pro file using: CONFIG […]