Common methods of QString

index at; returns the character at index i, or 0 if i exceeds the length of the string

const QString string( "abcdefgh" );
QChar ch = string.at( 4 );
	   

QString toLower() //Convert to lowercase
QString toUpper() //Convert to uppercase

QString c("cle");
QString str=c.toUpper();   // str == "cle"
qDebug()<<str;

tail insert append; push_back

Head insert prepend; push_front

QString cer = "data";
cer.append("list");
cer.push_back("yes");
cer.prepend("like");
cer.push_front("good");
qDebug()<<cer;

Basic type conversion

s1.toUInt();
s1.toDouble();
s1.toFloat();
s1.toShort();
s1.toLong();
s1.toULongLong();

length

s1.size()
s1.count();
s1.length();

Returns true if the string is zero. A zero string is always empty.

 QString a;          // a.unicode() == 0，a.length() == 0
 a.isNull();         // 真，因为a.unicode() == 0
 a.isEmpty();        // 真

Compare

 int a = QString::compare( "def", "abc" );   // a > 0
 int b = QString::compare( "abc", "def" );   // b < 0
 int c = QString::compare(" abc", "abc" );   // c == 0

Delete a character in the middle of a string

QString str = "Hello World!";
str.remove(5, 6);                   // str = "Hello!"

Insert character at specified position

QString str = "Hello!";
str.insert(5, QString(" World"));   // str = "Hello World!"

QString::number integer conversion

int a = 20;
uint b =255;
QString::number(a);
QString::number(a,10);
QString::number(b);
QString::number(b,16);

The above are simple examples commonly used by QString; more examples are waiting for us to explore!