TBoldAttribute¶

TBoldAttribute stores attribute values for Bold objects. Bold provides type-specific subclasses for different data types.

Class Hierarchy¶

classDiagram
    class TBoldMember {
        <<abstract>>
    }
    TBoldMember <|-- TBoldAttribute
    TBoldAttribute <|-- TBAString
    TBoldAttribute <|-- TBAInteger
    TBoldAttribute <|-- TBAFloat
    TBoldAttribute <|-- TBADateTime
    TBoldAttribute <|-- TBABoolean
    TBoldAttribute <|-- TBABlob

    TBoldAttribute : +IsNull
    TBoldAttribute : +SetToNull()
    TBoldAttribute : +AsString

    click TBoldMember href "../TBoldMember/" "TBoldMember documentation"
    click TBAString href "../TBAString/" "TBAString documentation"
    click TBAInteger href "../TBAInteger/" "TBAInteger documentation"
    click TBAFloat href "../TBAFloat/" "TBAFloat documentation"
    click TBABoolean href "../TBABoolean/" "TBABoolean documentation"
    click TBABlob href "../TBABlob/" "TBABlob documentation"

Attribute Types¶

Bold Type	Delphi Type	UML Type
`TBAString`	`string`	String
`TBAInteger`	`Integer`	Integer
`TBAFloat`	`Double`	Float, Currency
`TBAMoment`	`TDateTime`	DateTime, Date
`TBABoolean`	`Boolean`	Boolean
`TBABlob`	`TStream`	Blob
`TBACurrency`	`Currency`	Currency

Class Definition¶

TBoldAttribute = class(TBoldMember)
public
  // Null handling
  property IsNull: Boolean;
  procedure SetToNull;

  // Universal access
  property AsString: string;

  // Comparison
  function CompareToAs(Other: TBoldAttribute): Integer;
  function IsEqual(Other: TBoldAttribute): Boolean;
end;

// Type-specific classes
TBAString = class(TBoldAttribute)
public
  property AsString: string;
  property Length: Integer;
end;

TBAInteger = class(TBoldAttribute)
public
  property AsInteger: Integer;
end;

TBAFloat = class(TBoldAttribute)
public
  property AsFloat: Double;
end;

TBADateTime = class(TBoldAttribute)
public
  property AsDateTime: TDateTime;
end;

TBABoolean = class(TBoldAttribute)
public
  property AsBoolean: Boolean;
end;

Working with Attributes¶

Reading Values¶

var
  Name: string;
  Age: Integer;
  Salary: Double;
  HireDate: TDateTime;
  Active: Boolean;
begin
  Name := Customer.Name;
  Age := Customer.Age;
  Salary := Employee.Salary;
  HireDate := Employee.HireDate;
  Active := Customer.Active;
end;

Writing Values¶

Customer.Name := 'Acme Corp';
Customer.Age := 25;
Employee.Salary := 50000.00;
Employee.HireDate := Now;
Customer.Active := True;

Null Handling¶

// Check for null
if Customer.M_Email.IsNull then
  ShowMessage('No email');

// Set to null
Customer.M_Email.SetToNull;

// Use default value for null
var Email: string;
if Customer.M_Email.IsNull then
  Email := 'N/A'
else
  Email := Customer.Email;

Raw Member Access¶

Use M_ prefix for raw attribute access:

// Check null state
if Customer.M_Name.IsNull then ...

// Subscribe to changes
Customer.M_Name.DefaultSubscribe(Subscriber);

// Compare attributes
if Customer.M_Name.IsEqual(OtherCustomer.M_Name) then ...

Attribute Metadata¶

var
  Attr: TBoldAttribute;
  Info: TBoldMemberRTInfo;
begin
  Attr := Customer.M_Name;
  Info := Attr.BoldMemberRTInfo;

  Log('Name: ' + Info.ExpressionName);
  Log('Type: ' + Info.BoldType.ExpressionName);
  Log('Persistent: ' + BoolToStr(Info.IsPersistent, True));
end;

Derived Attributes¶

Attributes can be derived (calculated) from other values:

// In UML model, mark Total as derived
// Bold generates deriver code:

procedure TOrder._TotalDeriveAndSubscribe(DerivedObject: TObject;
  Subscriber: TBoldSubscriber);
begin
  // Subscribe to dependencies
  M_Quantity.DefaultSubscribe(Subscriber);
  M_UnitPrice.DefaultSubscribe(Subscriber);

  // Calculate
  M_Total.AsFloat := Quantity * UnitPrice;
end;

The derived value automatically updates when dependencies change.

Common Patterns¶

Safe Value Access¶

function SafeString(Attr: TBAString; Default: string = ''): string;
begin
  if Attr.IsNull then
    Result := Default
  else
    Result := Attr.AsString;
end;

// Usage
Email := SafeString(Customer.M_Email, 'no-email@example.com');

Format for Display¶

function FormatMoney(Attr: TBAFloat): string;
begin
  if Attr.IsNull then
    Result := '-'
  else
    Result := FormatFloat('$#,##0.00', Attr.AsFloat);
end;

Validate Before Save¶

procedure ValidateCustomer(Customer: TCustomer);
begin
  if Customer.M_Name.IsNull then
    raise Exception.Create('Name is required');

  if Customer.Name.Trim.IsEmpty then
    raise Exception.Create('Name cannot be empty');
end;