delphi中使用array结构体最好的例子
转自https://blog.csdn.net/qq_26657857/article/details/88733320
在开发中，能用结构体尽量不用类，因为结构体的存储机制是“栈”，这就意味着自动释放内存。但是在使用过程中也要注意以下几点：1.用完清空 2.用多少申请多少 下面用具体实例说明：
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;
type
TScore=record
course:string;
score:real;
end;
TPerson=record
Name:string;
ScoreList:array of TScore;
end;
TForm1 = class(TForm)
Memo1: TMemo;
Button1: TButton;
Button2: TButton;
Button3: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure showPeople(p:TPerson);
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
var
p:TPerson;
procedure TForm1.Button1Click(Sender: TObject);
begin
p.Name:=‘张三‘;
setlength(p.ScoreList,3);//有3门课程
p.ScoreList[0].course:=‘语文‘;
p.ScoreList[0].score:=98.5;
p.ScoreList[1].course:=‘数学‘;
p.ScoreList[1].score:=95;
p.ScoreList[2].course:=‘英语‘;
p.ScoreList[2].score:=87;
showPeople(p);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
p.Name:=‘李四‘;
setlength(p.ScoreList,3);//有3门课程
p.ScoreList[0].course:=‘语文‘;
p.ScoreList[0].score:=78.5;
p.ScoreList[1].course:=‘数学‘;
p.ScoreList[1].score:=70;
p.ScoreList[2].course:=‘英语‘;
p.ScoreList[2].score:=60;
showPeople(p);
end;
procedure TForm1.Button3Click(Sender: TObject);
begin
p.Name:=‘黄晓娜‘;
FillChar(p.ScoreList,sizeof(p.ScoreList),0); //这里清空缓存数据，生成 p.ScoreList=()
setlength(p.ScoreList,2);
//这种方法得到：p.ScoreList=((course=‘数学‘;score=78.5),(course=‘语文‘;score=70)) 采用截断模式
p.ScoreList[0].course:=‘语文‘;
p.ScoreList[0].score:=88.5;
p.ScoreList[1].course:=‘数学‘;
p.ScoreList[1].score:=90;
showPeople(p);
end;
procedure TForm1.showPeople(p: TPerson);
var
i:integer;
begin
memo1.Lines.Add(p.Name);
for I := Low(p.ScoreList) to High(p.ScoreList) do
begin
memo1.Lines.Add(format(‘%s:%.2f‘,[p.ScoreList[i].course,p.ScoreList[i].score]));
end;
end;
end.
说明：
综合上面的问题，如果采用setLength()方法来设置数组，容易因为缓存之前的数据未被更新而产生错误数据，最好使用fillChar()
方法进行清空后再申请。好比在使用FDStoreProcedure fdSp 实例对像时，使用前要 fdSp.Close; fdSp.Parameters.clear; 清空参数列表一样，这样更安全些。