[log book]C++ struct指標一直出現「變數尚未初始化」的訊息

─ 狀況說明

下面程式碼一直出現「變數尚未初始化」的錯誤訊息

void main()

{

        InspectionRegion *test;

        test->regionHeight = 10;

        test->startPointsOfEachRow = new hsPoint[10];

        test->endPointsOfEachRow = new hsPoint[10];

        

        for (int i = 0; i < 10; i++)

        {

               (test->startPointsOfEachRow + i)->X = i;

               (test->startPointsOfEachRow + i)->Y = i + 10;

               (test->endPointsOfEachRow + i)->X = i + 20;

               (test->endPointsOfEachRow + i)->Y = i + 30;

        }

}

─ 想法

我一開始以為是没把那塊記憶體歸零，後來才想起來，是我没有將結構指標指向該結構！

所謂的指標的型態，是代表這個指標指向什麼資料型態的變數，而我只是宣告了一個指向InspectionRegion這個結構的指標，並没指向任何InspectionRegion的結構，所以這時候要用new算子向記憶體要一個InspectionRegion的空間，並將指標指過去。

─ 程式碼

typedef struct

{

        int X;

        int Y;

}hsPoint;

typedef struct

{

        int regionHeight;

        hsPoint *startPointsOfEachRow;

        hsPoint *endPointsOfEachRow;

}InspectionRegion;

void main()

{

        InspectionRegion *test = new InspectionRegion;

        test->regionHeight = 10;

        test->startPointsOfEachRow = new hsPoint[10];

        test->endPointsOfEachRow = new hsPoint[10];

        

        for (int i = 0; i < 10; i++)

        {

               (test->startPointsOfEachRow + i)->X = i;

               (test->startPointsOfEachRow + i)->Y = i + 10;

               (test->endPointsOfEachRow + i)->X = i + 20;

               (test->endPointsOfEachRow + i)->Y = i + 30;

        }

}

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