References:
> PBNeo4jDemo example provided with the installer
> Neo4j native documentation, Cypher query syntax
After installation, a group PyBridge will appear in the Tool Palette of Delphi, where you can find the new components TPBNeo4j.
New component PBClient for Neo4j can be found in the Tool Palette under PyBridge group
Place TPBNeo4j onto the form and set up its main properties:
- BaseName – the default base name. You must set a new parameter value in the code each time you are going to work with a different database.
- BaseURL – the URL to connect to Neo4j
- Login and Password to access your database if required
Now PBClient for Neo4j is ready to be used. PBClient for Neo4j provides entire Neo4j query syntax based on Cypher. In addition, PBClient for Neo4j has special tools for the most used Cypher commands for nodes and edges, such as: CREATE, MATCH and DELETE. To demonstrate how it works, let’s create a simple application to manage the nodes and edges of the Neo4j database. Add the corresponding Buttons, Edits and Memo to your form:
In ‘GRAPH_NODE_CREATE’ and ‘GRAPH_NODE_MATCH’ ButtonClick event handler procedures we are using following PBNeo4j functions:
When providing a JSON string as function parameter, you can use single quotes instead of double quotes:
‘{“key_str”: “value_str”, …}’ – double quotes
‘{”key_str”: ”value_str”, …}’ – escaped single quotes
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procedure TForm2.GRAPH_NODE_CREATEClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBNeo4j1.GRAPH_NODE_CREATE('Person', '{"name": "Alice", "age": 23, "hair": "blonde"}');
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBNeo4j1.GRAPH_NODE_CREATE('Person', '{"name": "Alice", "age": 27, "hair": "brown"}');
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBNeo4j1.GRAPH_NODE_CREATE('Person', '{"name": "Kurt", "age": 27}');
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBNeo4j1.GRAPH_NODE_CREATE('Movie', '{"name": "Wall Street"}');
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
end
procedure TForm2.GRAPH_NODE_MATCHClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBNeo4j1.GRAPH_NODE_MATCH('Person', '{"name": "Alice", "hair": "blonde"}', ['name', 'age']);
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBNeo4j1.GRAPH_NODE_MATCH('Person', '{"name": "Alice", "age": 23}', ['name', 'hair']);
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Memo1.Lines.Append('')
end;
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To delete a node we should provide its ID to the GRAPH_NODE_DELETE function.
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procedure TForm2.GRAPH_NODE_DELETEClick(Sender: TObject);
begin
if trim(EditDelNode.Text) = '' then
exit;
PBNeo4j1.GRAPH_NODE_DELETE(StrToInt(EditDelNode.Text))
end;
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In ‘GRAPH_EDGE_CREATE’ and ‘GRAPH_EDGE_MATCH’ ButtonClick event handler procedures we are using following PBNeo4j functions:
- GRAPH_EDGE_CREATE(source_int, destination_int, ‘label’, ‘{“key_str”: “value_str”, “key_int”: value_int, …, “key_n”:”value_n”}’) – based on native CREATE this function creates a new ‘label’ edge between source and destination nodes with corresponding ‘{“key”:”value”}’ pairs.
- GRAPH_EDGE_MATCH(‘label’, ‘{“key_1”: “value_1”, …, “key_n”: “value_n”}’, [‘key_1’, …, ‘key_n’]) – based on native MATCH this function searches for all the ‘label’ edges with matching ‘{“key”:”value”}’ pairs, and returns values of selected [‘keys’].
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procedure TForm2.GRAPH_EDGE_CREATEClick(Sender: TObject);
var
Rslt, jres: string;
begin
if (trim(SourceID.Text) = '') or (trim(EndID.Text) = '') then
exit;
Rslt:= PBNeo4j1.GRAPH_EDGE_CREATE(StrToInt(SourceID.Text), StrToInt(EndID.Text), 'FRIENDS', '{"duration": ' + cnt.ToString + '}');
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
cnt := cnt + 1;
end;
procedure TForm2.GRAPH_EDGE_MATCHClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBNeo4j1.GRAPH_EDGE_MATCH('FRIENDS', '{"duration": ' + cnt.ToString + '}', ['duration']);
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Memo1.Lines.Append('')
end;
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To delete an edge we should provide its ID to the GRAPH_EDGE_DELETE function.
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procedure TForm2.GRAPH_EDGE_DELETEClick(Sender: TObject);
begin
if trim(EditDelEdge.Text) = '' then
exit;
PBRedisGraph1.GRAPH_EDGE_DELETE(StrToInt(EditDelEdge.Text))
end;
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The most powerful function of PBNeo4j is GRAPH_QUERY. Based on native QUERY this function can execute any Cypher language query that is supported by Neo4j.
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procedure TForm2.ButtonQueryClick(Sender: TObject);
var
Rslt, jres: string;
begin
if trim(EditQuery.Text) = '' then
exit;
Rslt := PBNeo4j1.GRAPH_QUERY(trim(EditQuery.Text));
jres := PBNeo4j1.res2dic(Rslt);
Memo1.Lines.Append((jres.Replace('},{', '},' + #13#10 + '{').Replace('rslt":[', 'Result":[' + #13#10)));
Memo1.Lines.Append('')
end;
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Below are some sample commands for you to try. Feel free to experiment with your own requests.
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MATCH (n) RETURN *
MATCH (n)-[r]-() RETURN r
MATCH (a:Person) WHERE a.name = 'Kurt' CREATE (a)-[:MEMBER]->(:Band {name:'Nirvana'})
CREATE (jim:Person{name:'Jim', age:29})-[:FRIENDS]->(pam:Person {name:'Pam', age:27})-[:WORKS]->(:Employer {name:'Dunder Mifflin'})
MATCH (:Person {name:'Jim'})-[r:FRIENDS]->() DELETE r
MATCH (n) DELETE n
MATCH (n:Person{name: 'Alice', hair: 'blonde'}) RETURN n.name, n.age
MATCH (n:Person{name: 'Alice', age: 23}) RETURN n.name, n.hair
MATCH ()-[r:FRIENDS]->() WHERE r.duration=3 RETURN r.duration
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This example demonstrates how easy it is to develop Delphi applications relying on Neo4j with a help of PBClient for Neo4j. Now you can also enjoy the full power of Neo4j in your applications!
