标签:io os ar 使用 for sp on cti bs
原本一直使用 TList, 将定义的一个个 Record 保存在TList 里面, 为了能把某些对象管理起来, 例如一个类的 n 多实例,可以进行索引、查找、释放等
今天刚看到原来已经有了一个叫 TDictionary 对象,用起来挺方便。 挺像我们在DB中定义的 Dictionary 表,Key、Value。 而那个不管Key、Value 都挺发达,允许各种定义的类。
ok,下面官方Demo很通俗易懂,各方法都在:
type
TCity = class
Country: String;
Latitude: Double;
Longitude: Double;
end;
const
EPSILON = 0.0000001;
var
Dictionary: TDictionary<String, TCity>;
City, Value: TCity;
Key: String;
begin
{ Create the dictionary. }
Dictionary := TDictionary<String, TCity>.Create;
City := TCity.Create;
{ Add some key-value pairs to the dictionary. }
City.Country := ‘Romania‘;
City.Latitude := 47.16;
City.Longitude := 27.58;
Dictionary.Add(‘Iasi‘, City);
City := TCity.Create;
City.Country := ‘United Kingdom‘;
City.Latitude := 51.5;
City.Longitude := -0.17;
Dictionary.Add(‘London‘, City);
City := TCity.Create;
City.Country := ‘Argentina‘;
{ Notice the wrong coordinates }
City.Latitude := 0;
City.Longitude := 0;
Dictionary.Add(‘Buenos Aires‘, City);
{ Display the current number of key-value entries. }
writeln(‘Number of pairs in the dictionary: ‘ +
IntToStr(Dictionary.Count));
// Try looking up "Iasi".
if (Dictionary.TryGetValue(‘Iasi‘, City) = True) then
begin
writeln(
‘Iasi is located in ‘ + City.Country +
‘ with latitude = ‘ + FloatToStrF(City.Latitude, ffFixed, 4, 2) +
‘ and longitude = ‘ + FloatToStrF(City.Longitude, ffFixed, 4, 2)
);
end
else
writeln(‘Could not find Iasi in the dictionary‘);
{ Remove the "Iasi" key from dictionary. }
Dictionary.Remove(‘Iasi‘);
{ Make sure the dictionary‘s capacity is set to the number of entries. }
Dictionary.TrimExcess;
{ Test if "Iasi" is a key in the dictionary. }
if Dictionary.ContainsKey(‘Iasi‘) then
writeln(‘The key "Iasi" is in the dictionary.‘)
else
writeln(‘The key "Iasi" is not in the dictionary.‘);
{ Test how (United Kingdom, 51.5, -0.17) is a value in the dictionary but
ContainsValue returns False if passed a different instance of TCity with the
same data, as different instances have different references. }
if Dictionary.ContainsKey(‘London‘) then
begin
Dictionary.TryGetValue(‘London‘, City);
if (City.Country = ‘United Kingdom‘