QT6 源（60）篇三：阅读与注释 QString 这个类，先给出其应用举例， split（）拆分成多个 QString，fromLatin1（）、number（）、toDouble（）、

（3）

++上面的函数太大，下面给出举例：

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++给出上图中的函数的源码依据 ：

// note - this are all inline so we can benefit from
    //strlen() compile time optimizations     以下全是静态的成员函数
    static        QString fromLatin1(     QByteArrayView    ba);
    Q_WEAK_OVERLOAD
    static inline QString fromLatin1(const QByteArray     & ba)
    { return fromLatin1(QByteArrayView(ba)); }

    //Returns a QString initialized with the first size characters of the
    //Latin-1 string str.
    //If size is -1, strlen(str) is used instead.
    static inline QString fromLatin1(const char * str, qsizetype size)
    {
        return fromLatin1(QByteArrayView(str, !str || size < 0
                                                ? qstrlen(str) : size));
    }

    static        QString fromUtf8(      QByteArrayView   utf8);
    Q_WEAK_OVERLOAD
    static inline QString fromUtf8(const QByteArray     & ba  )
    { return fromUtf8(QByteArrayView(ba)); }

    static inline QString fromUtf8(const char           * utf8, qsizetype size)
    {
        return fromUtf8(QByteArrayView(utf8, !utf8 || size < 0
                                               ? qstrlen(utf8) : size));
    }

    static        QString fromLocal8Bit(      QByteArrayView   ba);
    Q_WEAK_OVERLOAD
    static inline QString fromLocal8Bit(const QByteArray     & ba)
    { return fromLocal8Bit(QByteArrayView(ba)); }

    static inline QString fromLocal8Bit(const char           * str, qsizetype size)
    {
        return fromLocal8Bit(QByteArrayView(str, !str || size < 0
                                                   ? qstrlen(str) : size));
    }

（4）介绍另一个重要的静态函数， number（）：

    //Sets the string to the printed value of n in the specified base,
    //and returns a reference to the string.
    //The base is 10 by default and must be between 2 and 36.
    //The formatting always uses QLocale::C, i.e., English/UnitedStates.
    //To get a localized string representation of a number,
    //use QLocale::toString() with the appropriate locale.
    QString & setNum(short    n, int base=10)
    { return setNum(qlonglong(n), base); }

    QString & setNum(ushort   n, int base=10)
    { return setNum(qulonglong(n), base); }

    QString & setNum(int      n, int base=10)
    { return setNum(qlonglong(n), base); }

    QString & setNum(uint     n, int base=10)
    { return setNum(qulonglong(n), base); }

    QString & setNum(long     n, int base=10)
    { return setNum(qlonglong(n), base); }

    QString & setNum(ulong    n, int base=10)
    { return setNum(qulonglong(n), base); }

    QString & setNum(qlonglong , int base=10);
    QString & setNum(qulonglong, int base=10);

    QString & setNum(float n, char format='g', int precision=6)
    { return setNum(double(n),format,precision); }

    QString & setNum(double,  char format='g', int precision=6);
    //Sets the string to the printed value of n,
    //formatted according to the given format and precision,
    //and returns a reference to the string.
    
    //Returns a string equivalent of the number n according to the specified base.
    //The base is 10 by default and must be between 2 and 36.
    //For bases other than 10, n is treated as an unsigned integer.
    //The formatting always uses QLocale::C, i.e., English/UnitedStates.
    //To get a localized string representation of a number,
    //use QLocale::toString() with the appropriate locale.
    static QString number(int, int base=10);
    static QString number(uint, int base=10);
    static QString number(long, int base=10);
    static QString number(ulong, int base=10);
    static QString number(qlonglong, int base=10);
    static QString number(qulonglong, int base=10);
    static QString number(double n, char format='g', int precision=6);
    //Returns a string representing the floating-point number.
    //Returns a string that represents n,
    //formatted according to the specified format and precision.
    //For formats with an exponent,
    //the exponent will show its sign and have at least two digits,
    //left-padding the exponent with zero if needed.

++实验举例：

（5）接着介绍字符串到数值的转换函数：

//Returns the string converted to an int using base base,
    //which is 10 by default and must be between 2 and 36, or 0.
    //Returns 0 if the conversion fails.
    //If ok is not nullptr, failure is reported by setting *ok to false,
    //and success by setting *ok to true.
    //If base is 0, the C language convention is used:
    //If the string begins with "0x", base 16 is used;
    //if the string begins with "0", base 8 is used; otherwise, base 10 is used.
    //The string conversion will always happen in the 'C' locale.
    //For locale-dependent conversion use QLocale::toInt()
    short      toShort    (bool * ok=nullptr, int base = 10) const
    { return toIntegral_helper<short>(*this, ok, base); }
    
    ushort     toUShort   (bool * ok=nullptr, int base = 10) const
    { return toIntegral_helper<ushort>(*this, ok, base); }
    
    int        toInt      (bool * ok=nullptr, int base = 10) const
    { return toIntegral_helper<int>(*this, ok, base); }
    
    uint       toUInt     (bool * ok=nullptr, int base = 10) const
    { return toIntegral_helper<uint>(*this, ok, base); }
    
    long       toLong     (bool * ok=nullptr, int base = 10) const
    { return toIntegral_helper<long>(*this, ok, base); }
    
    ulong      toULong    (bool * ok=nullptr, int base = 10) const
    { return toIntegral_helper<ulong>(*this, ok, base); }
    
    qlonglong  toLongLong (bool * ok=nullptr, int base = 10) const;
    qulonglong toULongLong(bool * ok=nullptr, int base = 10) const;
    float      toFloat    (bool * ok=nullptr               ) const;
    double     toDouble   (bool * ok=nullptr               ) const;

++ 举例：

（6）

谢谢