QString字符串相关操作

1. 使用某个字符填满字符串，也就是说字符串里的所有字符都有等长度的ch来替代。

   QString::fill(QChar ch, int size=-1)

	QString str = "Berlin";
    str.fill('z');	//str == "zzzzzz"
    str.fill('A', 2); 	//str == "AA"

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2. 从字符串里查找相同的某个字符串str

   int QString::indexOf ( const QString & str, int from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive ) const

 	QString x = "sticky question";
 	QString y = "sti";
 	x.indexOf(y);               // returns 0
 	x.indexOf(y, 1);            // returns 10
 	x.indexOf(y, 10);           // returns 10
 	x.indexOf(y, 11);           // returns -1

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3. 指定位置插入字符串

   QString & QString::insert ( int position, const QString & str )

 	QString str = "Meal";
 	str.insert(1, QString("ontr"));
 	// str == "Montreal"

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4. 判断字符串是否为空
   bool QString::isEmpty () const

 	QString().isEmpty();            // returns true
 	QString("").isEmpty();          // returns true
 	QString("x").isEmpty();         // returns false
 	QString("abc").isEmpty();       // returns false

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5. 判断字符串是否存在

   bool QString::isNull () const

 	QString().isNull();             // returns true
 	QString("").isNull();           // returns false
 	QString("abc").isNull();        // returns false

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6. 左向右截取字符串
   QString QString::left ( int n ) const

 	QString x = "Pineapple";
 	QString y = x.left(4);      // y == "Pine"

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7. 从中间截取字符串
   QString QString::mid ( int position, int n = -1 ) const

 	QString x = "Nine pineapples";
 	QString y = x.mid(5, 4);            // y == "pine"
 	QString z = x.mid(5);               // z == "pineapples"

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8. 删除字符串中间某个字符
   QString & QString::remove ( int position, int n )

 	QString s = "Montreal";
	s.remove(1, 4);
 	// s == "Meal"

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9. 替换字符串中的某些字符
   QString & QString::replace ( int position, int n, const QString & after )

 	QString x = "Say yes!";
 	QString y = "no";
 	x.replace(4, 3, y);
 	// x == "Say no!"

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10. 以某个字符切割字符串
    QString QString::section ( QChar sep, int start, int end = -1, SectionFlags flags = SectionDefault ) const

	QString str;
	QString csv = "forename,middlename,surname,phone";
	QString path = "/usr/local/bin/myapp"; // First field is empty
	QString::SectionFlag flag = QString::SectionSkipEmpty;

	str = csv.section(',', 2, 2);   // str == "surname"
	str = path.section('/', 3, 4);  // str == "bin/myapp"
	str = path.section('/', 3, 3, flag); // str == "myapp"

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11. 把整形、浮点型或其他类型转换为QString
    QString & QString::setNum ( uint n, int base = 10 )

相类似的还有好多重载函数，想深入了解，还是要看Qt帮助文档的。