Smalltalk and Object Orientation: an Introduction - Free

Notice that in this example we used the message nextPutAll: to save the single string ‘Hello
World’. Remember that strings are actually collections and what this says is save the whole contents of
this collection to the file.
An important point to note about files is that it may sometimes be necessary to access a file which is
in a different directory to the working directory. This can be a cause of problems when porting between
platforms unless care is taken. If you hard code the name of a directory structure into your system then
you will need to modify the system code before it will work on a different platform. There is a way
around this using the construct: message. This constructs a path name which is appropriate for the
platform on which you are working. For example:
(('dcs' asFilename construct: 'jjh')
construct: 'visual' )
construct: 'examples'.
Try typing the above into a Workspace and inspecting the result. The actual pathname you obtain will
depend on your host operating system. For example, on a Windows -95 PC you shou ld see the style of
pathname illustrated in Figure 13.3.
Other messages which may be of use include:
Figure 13.3: Inspecting a filename on a PC
• directory Return the directory containing the receiving file.
• isDirectory Check to see if a filename is actually a directory.
It is also possible to obtain information on the date and time a file was modified, accessed or had its
status changed. To do this first use the message dates (this is another aspect which can differ from
one Smalltalk implementation to another). This is sent to a filename, which returns a dictionary of
associations. Then the key #modified will access the most recent modification, the key #accessed
will return the last access date and the key #statusChanged will provide the date of the most recent
change in the files status (or privileges). For example Figure 13.4 illustrates checking when a file was
last accessed, modified and its status changed.
Figure 13.4: Accessing a files details
The result of evaluating the code in Figure 13.4 on the temp.txt file created earlier might look like:
Last a ccess #(June 24, 1996 11:00:00 pm) Last modified #(June 25, 1996 1:56:54 pm)
Status changed nil
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