原型

QString QString::mid(int position, int n = -1) const

返回一个从position开始，长度为n的QString 类型的子串。 当position的下标值超出字符串长度时，返回null；当从position开始的子串长度不够n或n为-1（缺省时的默认值也为-1），函数返回从position开始到结尾的子串。

Returns a string that contains n characters of this string, starting at the specified position index. Returns a null string if the position index exceeds the length of the string. If there are less than n characters available in the string starting at the given position, or if n is -1 (default), the function returns all characters that are available from the specified position.

例子：

若需要QStringRef类型的子串，可以使用函数midRef （），与mid（）类似，只是返回类型为ref，原型如下

QStringRef QString::midRef(int position, int n = -1) const

返回一个从position开始，长度为n的类型的子串的引用。 当position的下标值超出字符串长度时，返回null引用；当从position开始的子串长度不够n或n为-1（缺省时的默认值也为-1），函数返回从position开始直到结尾的子串。

Returns a substring reference to n characters of this string, starting at the specified position. If the position exceeds the length of the string, a null reference is returned. If there are less than n characters available in the string, starting at the given position, or if n is -1 (default), the function returns all characters from the specified position onwards.

Example:

QString 还有left() 和 right().两个函数可以取子串

原型

QString QString::left(int n) const

返回最左边n个字符的子串。当n大于等于QString.size()或n小于0的时候，返回整个字符串。

Returns a substring that contains the n leftmost characters of the string. The entire string is returned if n is greater than or equal to size(), or less than zero.

例子：

right()与left()类似，不阐述