CString中找關鍵字的技巧

我們常常要在字串截取一段之後，尋找想要的一邊、一段、一個字。
在此，將使用MFC的CString做示範。(因為這個我最常用！XD）

CString技法

abcdefghijklmnopqrstuvwxyz
字串搜尋

• Find()函數

CString sample = “abcdefghijklmnopqrstuvwxyz”;
const CString goal(“fg”);
int goalIndex = sample.Find(goal);

 abcdefghijk…
0123456789…



• 找fg左全部

CString sample = “abcdefghijklmnopqrstuvwxyz”;
const CString goal(“fg”);
int goalIndex = sample.Find(goal);

CString result = sample.Left(goalIndex);

 abcdefghijk…
0123456789…



• 找fg左3位

CString sample = “abcdefghijklmnopqrstuvwxyz”;
const CString goal(“fg”);
int goalIndex = sample.Find(goal);
const int charAmount = 3;
CString result = sample.Mid(goalIndex-charAmount, charAmount);

 abcdefghijk…
0123456789…



• 取出特定字之間的字

CString sample = “abcdefghijklmnopqrstuvwxyz”;
const CString begin(“bc”), end(“fg”);
int beginIndex = sample.Find(begin);
int endIndex   = sample.Find(end);
CString result
    = sample.Mid(beginIndex+begin.GetLength(), 
        endIndex-beginIndex-begin.GetLength()); //感謝網友jordan5441更正

 abcdefghijk…
0123456789…



• 找fg右全部

CString sample = “abcdefghijklmnopqrstuvwxyz”;
const CString goal(“fg”);
int goalIndex = sample.Find(goal);

CString result 
  = sample.Right( sample.GetLength() -  goalIndex+goal.GetLength() );

 abcdefghijk…
0123456789…



• 找fg右3位

CString sample = “abcdefghijklmnopqrstuvwxyz”;
const CString goal(“fg”);
int goalIndex = sample.Find(goal);
const int charAmount = 3;
CString result = sample.Mid(abcIndex+goalIndex.GetLength(), charAmount);

 abcdefghijk…
0123456789…



• Find()注意事項

CString sample = “abcdefghijklmnopqrstuvwxyz”;
int errorIndex = sample.Find(“llllll”);
int emptyIndex = sample.Find(“”);

errorIndex: -1
emptyIndex: 0

搜尋空字串和找不到是兩件事。
也就是關鍵字搜尋(假設「找某關鍵字」為true)
「找某關鍵字or空字串」→true
「找某關鍵字and找不到」→false