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  • delphi 判断一个数组的长度用 Length 还是 SizeOf ?

    判断一个数组的长度用 Length 还是 SizeOf ?
    最近发现一些代码, 甚至有一些专家代码, 在遍历数组时所用的数组长度竟然是 SizeOf(arr); 这不合适!

    如果是一维数组、且元素大小是一个字节, 这样用看不出错误, 譬如:  
    --------------------------------------------------------------------------------

    var
    arr1: array[0..9] of Char;
    arr2: array[0..9] of Byte;
    begin
    ShowMessageFmt('%d,%d,%d,%d',[Length(arr1), SizeOf(arr1),
    Length(arr2), SizeOf(arr2)]);
    {显示结果: 10,10,10,10}
    end;
    --------------------------------------------------------------------------------
    但如果数组元素多于一个字节、或是多维数组的情况下, 就不行了, 举例:
    --------------------------------------------------------------------------------

    const
    arr1: array[0..9] of Integer = (1,2,3,4,5,6,7,8,9,10);
    arr2: array[0..1, 0..3] of Integer = ((1,2,3,4), (5,6,7,8));
    var
    arr3: array[Boolean] of Integer;
    arr4: array[Byte] of Integer;
    begin
    ShowMessage(IntToStr(Length(arr1))); {10}
    ShowMessage(IntToStr(SizeOf(arr1))); {40}

    ShowMessage(IntToStr(Length(arr2))); {2}
    ShowMessage(IntToStr(Length(arr2[0]))); {4}
    ShowMessage(IntToStr(Length(arr2[1]))); {4}
    ShowMessage(IntToStr(SizeOf(arr2))); {32}

    ShowMessage(IntToStr(Length(arr3))); {2}
    ShowMessage(IntToStr(SizeOf(arr3))); {8}

    ShowMessage(IntToStr(Length(arr4))); {256}
    ShowMessage(IntToStr(SizeOf(arr4))); {1024}
    end;
    --------------------------------------------------------------------------------
    我们倒是可以利用这个原理, 迅速知道多维数组的元素总数:
    --------------------------------------------------------------------------------

    const
    arr: array[0..1, 0..2, 0..3] of Integer = 
    (((1,1,1,1), (2,2,2,2), (3,3,3,3)), ((4,4,4,4), (5,5,5,5), (6,6,6,6)));
    begin
    ShowMessage(IntToStr(SizeOf(arr) div SizeOf(Integer))); {24}
    end;

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  • 原文地址:https://www.cnblogs.com/ilrc/p/5215105.html
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