VC中數據的動態交換技術DDV\DDX的實現方法

動態交換技術的實現依賴於幾個函數:
(1)void DoDataExchange(CDataExchange* pDX)
(2)BOOL UpdateData( BOOL bSaveAndValidate = TRUE );

DoDataExchange是功能的具體實現在.而UpdateData函數調用了DoDataExchange函數.
在程序中並沒有直接調用DoDataExchange函數,而是調用了UpdateData從而間接調用DoDataExchange函數.

動態交換數據是交一個控件與一個變量關聯起來,並且這個變量值的改變會影響到控件的顯示值,同時控件的顯示值的改變同樣會影響到這個變量的值.

在基於對話框的工程中,在OnInitDialog()和OnOK()函數中會調用UpdateData的函數，從而實現對控件的初始化及將控件的值保存起來。
UpdateData(FALSE)表示將變量值傳遞給控件即初始化控件；
UpdateData(TRUE)表示將控件的值傳遞給變量即將控件值保存起來；此時如果有設置範圍，就進行判斷值是否在規定的範圍內，不在則不保存數據並要求從新設置控件的值，在規定的範圍內則保存數據。

DDX_xxx：表示將一個控件與一個變量關聯起來，這個變量類型可以不同….
DDX_Text表示將編輯框與一個變量關聯起來
DDV_xxx: 表示設定這個變量值的範圍.

控件與變量的關聯是通過控件的ID來實現的。因此要確保在調用DoDataExchange之前確定控件的ID已經申請完成，即這個控件已經創建完成。
如果是動態創建的控件，它的ID號可事先在資源編輯中放置相同的控件後在刪除，這時在Resource.h中便可看到這類控件ID號的起始值是多少…動態創建的控件的ID號值只要遞增即可。

以下爲常用的動態交換數據的不同控件的交換函數
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, BYTE& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, short& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, int& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, UINT& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, long& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, DWORD& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, CString& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, LPTSTR value, int nMaxLen);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, float& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, double& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, COleCurrency& value);
void AFXAPI DDX_Text(CDataExchange* pDX, int nIDC, COleDateTime& value);
// special control types
void AFXAPI DDX_Check(CDataExchange* pDX, int nIDC, int& value);
void AFXAPI DDX_Radio(CDataExchange* pDX, int nIDC, int& value);
void AFXAPI DDX_LBString(CDataExchange* pDX, int nIDC, CString& value);
void AFXAPI DDX_CBString(CDataExchange* pDX, int nIDC, CString& value);
void AFXAPI DDX_LBIndex(CDataExchange* pDX, int nIDC, int& index);
void AFXAPI DDX_CBIndex(CDataExchange* pDX, int nIDC, int& index);
void AFXAPI DDX_LBStringExact(CDataExchange* pDX, int nIDC, CString& value);
void AFXAPI DDX_CBStringExact(CDataExchange* pDX, int nIDC, CString& value);
void AFXAPI DDX_Scroll(CDataExchange* pDX, int nIDC, int& value);
void AFXAPI DDX_Slider(CDataExchange* pDX, int nIDC, int& value);
void AFXAPI DDX_MonthCalCtrl(CDataExchange* pDX, int nIDC, CTime& value);
void AFXAPI DDX_MonthCalCtrl(CDataExchange* pDX, int nIDC, COleDateTime& value);
void AFXAPI DDX_DateTimeCtrl(CDataExchange* pDX, int nIDC, CTime& value);
void AFXAPI DDX_DateTimeCtrl(CDataExchange* pDX, int nIDC, COleDateTime& value);
// for getting access to the actual controls
void AFXAPI DDX_Control(CDataExchange* pDX, int nIDC, CWnd& rControl);
/////////////////////////////////////////////////////////////////////////////
// Standard Dialog Data Validation routines
// range - value must be >= minVal and <= maxVal
// NOTE: you will require casts for ‘minVal’ and ‘maxVal’ to use the
// UINT, DWORD or float types
void AFXAPI DDV_MinMaxByte(CDataExchange* pDX, BYTE value, BYTE minVal, BYTE maxVal);
void AFXAPI DDV_MinMaxShort(CDataExchange* pDX, short value, short minVal, short maxVal);
void AFXAPI DDV_MinMaxInt(CDataExchange* pDX, int value, int minVal, int maxVal);
void AFXAPI DDV_MinMaxLong(CDataExchange* pDX, long value, long minVal, long maxVal);
void AFXAPI DDV_MinMaxUInt(CDataExchange* pDX, UINT value, UINT minVal, UINT maxVal);
void AFXAPI DDV_MinMaxDWord(CDataExchange* pDX, DWORD value, DWORD minVal, DWORD maxVal);
void AFXAPI DDV_MinMaxFloat(CDataExchange* pDX, float const& value, float minVal, float maxVal);
void AFXAPI DDV_MinMaxDouble(CDataExchange* pDX, double const& value, double minVal, double maxVal);
// special control types
void AFXAPI DDV_MinMaxSlider(CDataExchange* pDX, DWORD value, DWORD minVal, DWORD maxVal);
void AFXAPI DDV_MinMaxDateTime(CDataExchange* pDX, CTime& refValue, const CTime* refMinRange, const CTime* refMaxRange);
void AFXAPI DDV_MinMaxDateTime(CDataExchange* pDX, COleDateTime& refValue, const COleDateTime* refMinRange, const COleDateTime* refMaxRange);
void AFXAPI DDV_MinMaxMonth(CDataExchange* pDX, CTime& refValue, const CTime* pMinRange, const CTime* pMaxRange);
void AFXAPI DDV_MinMaxMonth(CDataExchange* pDX, COleDateTime& refValue, const COleDateTime* refMinRange, const COleDateTime* refMaxRange);