Rss Xojo Plugin Reference Documentation

Rss

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.

Object Creation

Dim rss As New Chilkat.Rss

Properties

DebugLogFilePath As String

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.

LastErrorHtml As String (read-only)

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.

LastErrorText As String (read-only)

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.

Concept of LastErrorText

LastErrorText Standard Information

LastErrorXml As String (read-only)

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.

LastMethodSuccess As Boolean

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of True indicates success, a value of False 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 = True and failure = False.
  • 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 True. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

NumChannels As Int32 (read-only)

The number of channels in the RSS document.

NumItems As Int32 (read-only)

The number of items in the channel.

VerboseLogging As Boolean

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

Version As String (read-only)

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

Methods

Function AddNewChannel() As Chilkat.Rss

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

Returns Nil on failure

Function AddNewImage() As Chilkat.Rss

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

Returns Nil on failure

Function AddNewItem() As Chilkat.Rss

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

Returns Nil on failure

Function DownloadRss(url As String) As Boolean

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

Returns True for success, False for failure.

Example: Read RSS Feed

Function DownloadRssAsync(url As String) As Chilkat.Task

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.

Returns Nil on failure

How to Run an Asynchronous Task

Function GetAttr(tag As String, attrName As String) As String

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 Nil on failure

Function GetChannel(index As Int32) As Chilkat.Rss

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.

Returns Nil on failure

Function GetCount(tag As String) As Int32

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

Function GetDateStr(tag As String) As String

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

Returns Nil on failure

Function GetImage() As Chilkat.Rss

Return the image associated with the channel.

Returns Nil on failure

Function GetInt(tag As String) As Int32

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

Function GetItem(index As Int32) As Chilkat.Rss

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

Returns Nil on failure

Function GetString(tag As String) As String

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

Returns Nil on failure

Function LoadRssFile(filePath As String) As Boolean

Load an RSS document from a file.

Returns True for success, False for failure.

Function LoadRssString(rssString As String) As Boolean

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

Returns True for success, False for failure.

Function MGetAttr(tag As String, index As Int32, attrName As String) As String

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 Nil on failure

Function MGetString(tag As String, index As Int32) As String

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

Returns Nil on failure

Function MSetAttr(tag As String, idx As Int32, attrName As String, value As String) As Boolean

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

Returns True for success, False for failure.

Function MSetString(tag As String, idx As Int32, value As String) As Boolean

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

Returns True for success, False for failure.

Sub NewRss()

Clears the RSS document.

Sub Remove(tag As String)

Removes a sub-element from the RSS document.

Function SaveLastError(path As String) As Boolean

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns True for success, False for failure.

Sub SetAttr(tag As String, attrName As String, value As String)

Sets the value of a sub-element attribute.

Sub SetDateNow(tag As String)

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

Sub SetDateStr(tag As String, dateTimeStr As String)

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

Sub SetInt(tag As String, value As Int32)

Sets the value of an integer sub-element.

Sub SetString(tag As String, value As String)

Sets the value of a sub-element.

Function ToXmlString() As String

Returns the RSS document as an XML string.

Returns Nil on failure

Events

To implement events, your application would define and implement a class that is a subclass of Chilkat.Rss. Your custom class would implement (i.e. override) some or all of the event methods.

For example:

class MyRss
    Inherits Chilkat.Rss

    Function AbortCheck() As Boolean

    Sub BinaryData(data As MemoryBlock)

    Function PercentDone(pctDone As Int32) As Boolean

    Sub ProgressInfo(name As String, value As String)

    Sub TaskCompleted(task As Chilkat.Task)

    Sub TextData(data As String)


End Class

Function AbortCheck() As Boolean

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.

Sub BinaryData(data As MemoryBlock)

Binary data provided by certain methods.

Function PercentDone(pctDone As Int32) As Boolean

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.

The abort output argument provides a means for aborting the operation. Setting it to True will cause the method to abort and return a failed status (or whatever return value indicates failure).

Sub ProgressInfo(name As String, value As String)

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.

Sub TaskCompleted(task As Chilkat.Task)

Called in the background thread when an asynchronous task completes.

Sub TextData(data As String)

Text data provided by certain methods.