TArrayErrorsStack

Table of contents

• About
• TOptionalError
• Create
• Push
• Pop
• Count
• Iterate
  • FirstEntry
  • TIterator
    • HasValue
    • Next
    • Value

About

TArrayErrorsStack is generic stack over array of T which contains errors codes.

uses
utils.errorsstack;
typegeneric TArrayErrorsStack<T> = class

TOptionalError

If macro {$USE_OPTIONAL} is defined, then all methods return a TOptional wrapper, otherwise T.

uses
utils.optional;
type
TOptionalError = {$IFDEF FPC}specialize{$ENDIF} TOptional<T>;

For non-existent values, returns a empty TOptionalError if defined or an EErrorNotExists is thrown.

type{$IFNDEF USE_OPTIONAL}
EErrorNotExists = class(Exception);
{$ENDIF}

Create

A new array error stack can be created by call its constructor.

constructor Create;

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
begin
errors := TErrors.Create;
FreeAndNil(errors);
end;

Push

Push error to stack.

procedurePush (AError : T);

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
const
SOMETHING_WRONG = 1;
var
errors : TErrors;
begin
errors := TErrors.Create;
errors.Push(SOMETHING_WRONG);
FreeAndNil(errors);
end;

Pop

Return top error and remove it from stack.

functionPop : {$IFNDEF USE_OPTIONAL}T{$ELSE}TOptionalError{$ENDIF};

If errors stack not contains values then returns empty TOptionalError or raise EErrorNotExists.

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
begin
errors := TErrors.Create;
writeln(errors.Pop);
FreeAndNil(errors);
end;

Count

Return stack count elements.

functionCount : LongInt;

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
begin
errors := TErrors.Create;
writeln(errors.Count);
FreeAndNil(errors);
end;

Iterate

It is possible to iterate for TArrayErrorsStack values using in operator. Each value would present as TArrayErrorsStack.TIterator object.

uses
utils.errorsstack;
typegeneric TArrayErrorsStack<T> = classtype
TIterator = class({$IFDEF FPC}specialize{$ENDIF} TForwardIterator<T, TIterator>)
end;

TForwardIterator is a abstract class which provide interface for iterable object that can moves to forward side.

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
value : Integer;
begin
errors := TErrors.Create;
forvaluein errors do
;
FreeAndNil(errors);
end;

FirstEntry

Retrive the iterator for first entry in an array errors stack.

functionFirstEntry : TIterator;

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
iterator : TErrors.TIterator;
begin
errors := TErrors.Create;
iterator := errors.FirstEntry;
FreeAndNil(errors);
end;

TIterator

HasValue

Return true if iterator has correct value.

functionHasValue : Boolean;

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
iterator : TErrors.TIterator;
begin
errors := TErrors.Create;
iterator := errors.FirstEntry;
while iterator.HasValue dobegin
iterator := iterator.Next;
end;
FreeAndNil(errors);
end;

Next

Retrieve the iterator for next entry in an array errors stack.

functionNext : TIterator;

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
iterator : TErrors.TIterator;
begin
errors := TErrors.Create;
iterator := errors.FirstEntry;
while iterator.HasValue dobegin
iterator := iterator.Next;
end;
FreeAndNil(errors);
end;

Value

To get value use Value property.

propertyValue : {$IFNDEF USE_OPTIONAL}V{$ELSE}TOptionalError{$ENDIF};

If iterator not have correct value returns empty TOptionalError or raise EErrorNotExists.

Example

uses
utils.errorsstack;
type
TErrors = {$IFDEF FPC}specialize{$ENDIF} TArrayErrorsStack<Integer>;
var
errors : TErrors;
iterator : TErrors.TIterator;
begin
errors := TErrors.Create;
iterator := errors.FirstEntry;
while iterator.HasValue dobegin
writeln(iterator.Value);
iterator := iterator.Next;
end;
FreeAndNil(errors);
end;