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Data Accessor Services and Locking Mechanism in Object-Oriented Programming

This structured system allows for state information with locked data access, validation, and conversion functions in OOP environment. Functions include adding/removing accessor, notifying changes, and managing locks.

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Data Accessor Services and Locking Mechanism in Object-Oriented Programming

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  1. TDataElement Minimum required state information: property DataLocked: Boolean; read only property DataLocker: TDataAccessor; read only property DataValid: Boolean; function DataToText: String; virtual procedure TextToData(TextRep: string); virtual Services for friends: procedure AddAccessor(Accessor: TDataAccessor); procedure RemoveAccessor(Accessor: TDataAccessor); procedure Notify(ChangeEvent: TChangeEvent); procedure GrabLock(Accessor: TDataAccessor); procedure ReleaseLock(Accessor: TDataAccessor); TDataAccessor Procedure Create(BaseUnits: String); property Value: Float; property BaseUnits: String; read only property DisplayUnits: String; function DataToText: String; override procedure TextToData(TextRep: String); override TNumData TNumAcc Create(ADataElement: TDataElement); property OnChange: TChangeEventHandler property DataValid: Boolean property Locked: Boolean; read only property Locker: TDataAccessor; read only property HoldsLock: Boolean; read only procedure GrabLock; procedure ReleaseLock; procedure Create(Anum: TNumData); property Value: Float; property Units: String; Key Inheritance Association Class

  2. OnTempChange: update display if AofTemp.Value out of limit then do user dialog try AofX.GrabLock; AofX.Value := user input; AofX.ReleaseLock; except Couldn’t get lock AofTemp: TNumAcc AofX: TNumAcc Wsht: TWorksheetAccerssorGateway Temp: TNumData AofTemp: TNumAcc X: TNumData AofTemp: TNumAcc if AofX.DataValid then AofTemp.Value:= 273.0+AofX.Value; AofX: TNumAcc AofX: TNumAcc Wizard UI Form Worksheet SubCalculation

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