Overview
The Candidate class is a domain entity that represents a candidate participating in an election. It encapsulates candidate profile information including name, party affiliation, and biography with controlled mutation through setters.
Constructor
new Candidate(
candidateID: string,
electionID: string,
name: string,
party: string,
biography: string
)
Unique identifier for the candidate
ID of the election the candidate is participating in
Full name of the candidate (cannot be empty)
Political party or affiliation of the candidate
Biographical information about the candidate
Example
const candidate = new Candidate(
"candidate-123",
"election-456",
"Jane Smith",
"Progressive Party",
"Jane Smith has 15 years of experience in public service..."
);
Properties
Unique identifier for the candidate (read-only)
ID of the election the candidate is participating in (read-only)
Full name of the candidate. Can be updated via setter with validation.
Political party or affiliation of the candidate. Can be updated via setter.
Biographical information about the candidate. Can be updated via setter.
Setters
name
Updates the candidate’s name with validation.
candidate.name = "Jane M. Smith";
- Throws
Error if name is empty or contains only whitespace
- Error message: “Candidate name cannot be empty”
party
Updates the candidate’s party affiliation.
candidate.party = "Independent";
biography
Updates the candidate’s biographical information.
candidate.biography = "Updated biography with more details...";
Usage Example
import { Candidate } from "./domain/entities/Candidate";
// Create a new candidate
const candidate = new Candidate(
"candidate-001",
"election-2024",
"John Doe",
"Democratic Party",
"John Doe is a community organizer with 10 years of experience."
);
// Access candidate information
console.log(candidate.candidateID); // "candidate-001"
console.log(candidate.name); // "John Doe"
console.log(candidate.party); // "Democratic Party"
// Update candidate information
candidate.name = "John M. Doe";
candidate.biography = "John M. Doe is a community organizer and advocate...";
// Change party affiliation
candidate.party = "Independent";
Validation Rules
Name Validation
The candidate name is validated when set:
const candidate = new Candidate(
"c1",
"e1",
"Initial Name",
"Party",
"Bio"
);
// Valid update
candidate.name = "Updated Name"; // ✓ Works
// Invalid updates
candidate.name = ""; // ✗ Throws: "Candidate name cannot be empty"
candidate.name = " "; // ✗ Throws: "Candidate name cannot be empty"
Party and Biography
Party and biography setters have no validation constraints:
// All of these are valid
candidate.party = "New Party"; // ✓ Works
candidate.party = ""; // ✓ Works (empty string allowed)
candidate.biography = "Updated bio"; // ✓ Works
candidate.biography = ""; // ✓ Works (empty string allowed)
Design Notes
Encapsulation
The Candidate entity uses TypeScript’s private fields with getter/setter pattern:
- Private fields (prefixed with
_): Store actual data
- Getters: Provide read access to all properties
- Setters: Control write access with validation where needed
This ensures:
- Data integrity through validation
- Controlled mutation of state
- Clear API for property access
Immutable Properties
The following properties are read-only after construction:
candidateID - Cannot be changed (no setter)electionID - Cannot be changed (no setter)
This prevents candidates from being reassigned to different elections or having their identifiers changed.
Common Use Cases
Adding Candidate to Election
import { Election } from "./domain/entities/Election";
import { Candidate } from "./domain/entities/Candidate";
import { ElectionType, ElectionStatus } from "./domain/enums";
const election = new Election(
"election-1",
"City Council Election",
ElectionType.FPTP,
new Date("2024-06-01"),
new Date("2024-06-15"),
"Annual city council election"
);
const candidate = new Candidate(
"candidate-1",
"election-1",
"Alice Johnson",
"Progressive Party",
"Community leader and educator"
);
// Add candidate to election (only works in DRAFT status)
election.addCandidate(candidate);
Updating Candidate Profile
// Update candidate information during campaign
candidate.biography = `${candidate.biography} Recently awarded Community Service Medal.`;
// Candidate switches to independent
candidate.party = "Independent";