Using Caché Objects - InterSystems Documentation

• CopyFrom — Copy the contents of a source stream into this stream.
• NewFileName — Specify a filename for a %FileCharacterStream or %FileBinaryStream
property.
Commonly used properties include the following:
• %Location — The default storage location (directory or global) where the stream will
store its persistent data. If no location is declared for a stream, the %Location for globals
will default to ^ooClassNameS, and the %Location for files will default to the current
Caché directory.
• AtEnd — Set to true when a Read encounters the end of the data source.
• Id — The unique identifier for an instance of a stream within the extent specified by
%Location.
• Size — The current size of the stream (in bytes or characters, depending on the type of
stream).
The following sections provide concrete examples using these methods and properties. For
detailed information on individual Stream methods and properties, see the Class Reference
entries for the classes listed at the beginning of this chapter.
15.2.1 Reading and Writing Stream Data
At the core of the Stream interface are the methods Read, Write, and Rewind and the properties
AtEnd and Size.
The following example reads data from the Person.Memo stream and writes it to the console,
100 characters at a time. The value of len is passed by reference, and is reset to 100 before
each Read. The Read method attempts to read the number of characters specified by len,
and then sets it to the actual number of characters read:
Do person.Memo.Rewind()
While (person.Memo.AtEnd = 0) {
Set len = 100
Write person.Memo.Read(.len)
}
Similarly, you can write data into the stream:
Do person.Memo.Write("This is some text. ")
Do person.Memo.Write("This is some more text.")
Using the Stream Interface
Using Caché Objects 135