今天剛看到原來已經有了壹個叫 TDictionary 對象，用起來挺方便。 挺像我們在DB中定義的 Dictionary 表，Key、Value。 而那個不管Key、Value 都挺發達，允許各種定義的類。
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') and (CompareValue(City.Latitude, 51.5, EPSILON) = EqualsValue) and (CompareValue(City.Longitude, -0.17, EPSILON) = EqualsValue) then
writeln('The value (United Kingdom, 51.5, -0.17) is in the dictionary.')
else
writeln('Error: The value (United Kingdom, 51.5, -0.17) is not in the dictionary.');
City := TCity.Create;
City.Country := 'United Kingdom';
City.Latitude := 51.5;
City.Longitude := -0.17;
if Dictionary.ContainsValue(City) then
writeln('Error: A new instance of TCity with values (United Kingdom, 51.5, -0.17) matches an existing instance in the dictionary.')
else
writeln('A new instance of TCity with values (United Kingdom, 51.5, -0.17) does not match any existing instance in the dictionary.');
City.Free;
end
else
writeln('Error: The key "London" is not in the dictionary.');
{ Update the coordinates to the correct ones. }
City := TCity.Create;
City.Country := 'Argentina';
City.Latitude := -34.6;
City.Longitude := -58.45;
Dictionary.AddOrSetValue('Buenos Aires', City);
{ Generate the exception "Duplicates not allowed". }
try
Dictionary.Add('Buenos Aires', City);
except
on Exception do
writeln('Could not add entry. Duplicates are not allowed.');
end;
{ Display all countries. }
writeln('All countries:');
for Value in Dictionary.Values do
writeln(Value.Country);
{ Iterate through all keys in the dictionary and display their coordinates. }
writeln('All cities and their coordinates:');
for Key in Dictionary.Keys do
begin
writeln(Key + ': ' + FloatToStrF(Dictionary.Items[Key].Latitude, ffFixed, 4, 2) + ', ' +
FloatToStrF(Dictionary.Items[Key].Longitude, ffFixed, 4, 2));
end;
{ Clear all entries in the dictionary. }
Dictionary.Clear;
{ There should be no entries at this point. }
writeln('Number of key-value pairs in the dictionary after cleaning: ' + IntToStr(Dictionary.Count));
{ Free the memory allocated for the dictionary. }
Dictionary.Free;
City.Free;
readln;
end.