TChilkatRss Delphi ActiveX Reference Documentation

TChilkatRss

Represents an RSS document or sub-part of a document such as a channel, image, or item. The RSS API allows one to download, create and modify RSS documents.

Importing the Chilkat ActiveX into Delphi

Important: Whenever upgrading to a new version of Chilkat, make sure to re-imported ActiveX DLL into Delphi to regenerate the files described below.

Two things are required to use an ActiveX in Delphi:

  1. The ActiveX DLL needs to be registered via regsvr32 on the system where the Delphi application runs. See How To Register ActiveX DLLs for detailed information.
  2. The ActiveX component needs to be "imported". Use the Delphi Import Component Wizard to import the Chilkat type library. This creates the following files: Chilkat_v9_5_0_TLB.pas and Chilkat_v9_5_0_TLB.dcr. The Chilkat_v9_5_0_TLB.pas should be added to your project.

To import the Chilkat type library, do the following:

  1. In the Delphi RAD Studio, select the menu item "Component" --> "Import a Type Library".
  2. Find "Chilkat ActiveX v9.5.0" in the list and select it. This will only appear in the list if the ChilkatAx-9.5.0-win32.dll (or ChilkatAx-9.5.0-x64.dll) has been registered w/ regsvr32.
  3. Check the "Generate Component Wrappers" checkbox.
  4. Select a directory where the unit files (.pas and .dcr) will be generated.
  5. Select "Create Unit" and then "Finish".
  6. Add the .pas to your Delphi project.

To use a Chilkat ActiveX object in your Delphi code, add "Chilkat_v9_5_0_TLB" to the "uses" statement. For example:

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_v9_5_0_TLB;

Object Creation

var
obj: TChilkatRss;
...
begin
obj := TChilkatRss.Create(Self);
...
// When finished, free the object instance.
obj.Free();

Properties

property DebugLogFilePath: WideString

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

property LastBinaryResult: OleVariant readonly

Introduced in version 9.5.0.52

The binary data returned by the last (binary data returning) method called. Only available if Chilkat.Global.KeepBinaryResult is set to 1. This provides a means for obtaining large varbinary results in the SQL Server environment (where limitations exist in getting large amounts of data returned by method calls, but where temp tables can be used for binary properties).

property LastErrorHtml: WideString readonly

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

property LastErrorText: WideString readonly

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

property LastErrorXml: WideString readonly

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

property LastMethodSuccess: Integer

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of 1 indicates success, a value of 0 indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = 1 and failure = 0.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to 1. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

property LastStringResult: WideString readonly

Introduced in version 9.5.0.52

The string return value of the last (string returning) method called. Only available if Chilkat.Global.KeepStringResult is set to 1. This provides a means for obtaining large string results in the SQL Server environment (where limitations exist in getting long strings returned by method calls, but where temp tables can be used for string properties).

Long Strings Returned by ActiveX Methods in SQL Server

property LastStringResultLen: Integer readonly

Introduced in version 9.5.0.53

The length, in characters, of the string contained in the LastStringResult property.

property NumChannels: Integer readonly

The number of channels in the RSS document.

property NumItems: Integer readonly

The number of items in the channel.

property VerboseLogging: Integer

If set to 1, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is 0. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

property Version: WideString readonly

Version of the component/library, such as "9.4.1.42"

Methods

function AddNewChannel(): TChilkatRss;

Adds a new channel to the RSS document. Returns the Rss object representing the Channel which can then be edited.

function AddNewImage(): TChilkatRss;

Adds a new image to the RSS document. Returns the Rss object representing the image, which can then be edited.

function AddNewItem(): TChilkatRss;

Adds a new Item to an Rss channel. Returns the Rss object representing the item which can then be edited.

function DownloadRss(url: WideString): Integer;

Downloads an RSS document from the Internet and populates the Rss object with the contents.

Returns 1 for success, 0 for failure.

Example: Read RSS Feed

function DownloadRssAsync(url: WideString): TChilkatTask;

Creates an asynchronous task to call the DownloadRss method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.

How to Run an Asynchronous Task

function GetAttr(tag: WideString; attrName: WideString): WideString;

Returns the value of a sub-element attribute. For example, to get the value of the "isPermaLink" attribute of the "guid" sub-element, call item.GetAttr("guid","isPermaLink").

Returns a zero-length WideString on failure

function GetChannel(index: Integer): TChilkatRss;

Returns the Nth channel of an RSS document. Usually there is only 1 channel per document, so the index argument should be set to 0.

function GetCount(tag: WideString): Integer;

Return the number of sub-elements with a specific tag.

function GetDate(tag: WideString): TDateTime;

This method is deprecated. It will be removed in a future version.

Return the value of a sub-element in date/time format.

function GetDateStr(tag: WideString): WideString;

The same as GetDate, except the date/time is returned in RFC822 string format.

Returns a zero-length WideString on failure

function GetImage(): TChilkatRss;

Return the image associated with the channel.

function GetInt(tag: WideString): Integer;

Return the value of a numeric sub-element as an integer.

function GetItem(index: Integer): TChilkatRss;

Return the Nth item of a channel as an RSS object.

function GetString(tag: WideString): WideString;

Return the value of an sub-element as a string.

Returns a zero-length WideString on failure

function LoadRssFile(filePath: WideString): Integer;

Load an RSS document from a file.

Returns 1 for success, 0 for failure.

function LoadRssString(rssString: WideString): Integer;

Loads an RSS feed document from an in-memory string.

Returns 1 for success, 0 for failure.

function MGetAttr(tag: WideString; index: Integer; attrName: WideString): WideString;

Get an attribute value for the Nth sub-element having a specific tag. As an example, an RSS item may have several "category" sub-elements. To get the value of the "domain" attribute for the 3rd category, call MGetAttr("category",2,"domain").

Returns a zero-length WideString on failure

function MGetString(tag: WideString; index: Integer): WideString;

Get the value of the Nth occurance of a sub-element. Indexing begins at 0.

Returns a zero-length WideString on failure

function MSetAttr(tag: WideString; idx: Integer; attrName: WideString; value: WideString): Integer;

Set an attribute on the Nth occurance of a sub-element.

Returns 1 for success, 0 for failure.

function MSetString(tag: WideString; idx: Integer; value: WideString): Integer;

Set the value of the Nth occurance of a sub-element. Indexing begins at 0.

Returns 1 for success, 0 for failure.

procedure NewRss();

Clears the RSS document.

procedure Remove(tag: WideString);

Removes a sub-element from the RSS document.

procedure SetAttr(tag: WideString; attrName: WideString; value: WideString);

Sets the value of a sub-element attribute.

procedure SetDate(tag: WideString; dateTime: TDateTime);

This method is deprecated. It will be removed in a future version.

Sets the value of a date/time sub-element.

procedure SetDateNow(tag: WideString);

Sets the value of a date/time sub-element to the current system date/time.

procedure SetDateStr(tag: WideString; dateTimeStr: WideString);

The same as SetDate, except the date/time is passed as an RFC822 string.

procedure SetInt(tag: WideString; value: Integer);

Sets the value of an integer sub-element.

procedure SetString(tag: WideString; value: WideString);

Sets the value of a sub-element.

function ToXmlString(): WideString;

Returns the RSS document as an XML string.

Returns a zero-length WideString on failure

Events

procedure AbortCheck(ASender: TObject; out abort: Integer);

Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200.

Delphi ActiveX Event callback implementation:

procedure TForm1.rssAbortCheck(ASender: TObject;  out abort: Integer);
begin
    // Application code goes here...
end;


procedure TForm1.Button1Click(Sender: TObject);
var
  rss: TChilkatRss;

begin
  rss := TChilkatRss.Create(Self);
  rss.OnAbortCheck := rssAbortCheck;
  // ...

procedure ProgressInfo(ASender: TObject; const name: WideString; const value: WideString);

A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.

Delphi ActiveX Event callback implementation:

procedure TForm1.rssProgressInfo(ASender: TObject;  const name: WideString; const value: WideString);
begin
    // Application code goes here...
end;


procedure TForm1.Button1Click(Sender: TObject);
var
  rss: TChilkatRss;

begin
  rss := TChilkatRss.Create(Self);
  rss.OnProgressInfo := rssProgressInfo;
  // ...

procedure TaskCompleted(ASender: TObject; const task: IChilkatTask);

Called in the background thread when an asynchronous task completes.

Delphi TaskCompleted Event Callback Example

Delphi ActiveX Event callback implementation:

procedure TForm1.rssTaskCompleted(ASender: TObject;  const task: IChilkatTask);
begin
    // Application code goes here...
end;


procedure TForm1.Button1Click(Sender: TObject);
var
  rss: TChilkatRss;

begin
  rss := TChilkatRss.Create(Self);
  rss.OnTaskCompleted := rssTaskCompleted;
  // ...