While I was trying to understand how to write code for the “deprecation” of “WriteError”, I noticed there wasn’t a Try Catch in the code.
I went looking for an explanation of when I need a Try Catch set of statements versus just Exception.
When I looked at Try Catch, it said for RuntimeException errors.
IOException is on that page, so I followed its link and got back to the beginning of the circle.
So. What’s the difference?
Here’s the code:
[code]Var f As FolderItem = FolderItem.ShowSaveFileDialog(FileTypes1.Text, “Create Example.txt”)
If f <> Nil Then
Var t As TextOutputStream = TextOutputStream.Create(f) // this line could raise an IOException.
t.WriteLine(TextField1.Value)
End If
Exception err As IOException
MsgBox(“an IO exception occurred”)[/code]
When you use try catch its often in the middle of code and there may be more code following the catch you want to continue executing
So you might see
... some bunch of code ...
try
<code that might raise an exception like an io error etc>
catch exc as <some type of exception>
end try
... some bunch of code ...
but then other times you have a tiny bit of code that doesnt have other code to follow so you just want to catch ALL exceptions and deal with them
You COULD write
try
Var f As FolderItem = FolderItem.ShowSaveFileDialog(FileTypes1.Text, "Create Example.txt")
If f <> Nil Then
Var t As TextOutputStream = TextOutputStream.Create(f) // this line could raise an IOException.
t.WriteLine(TextField1.Value)
End If
catch exc err As IOException
MsgBox("an IO exception occurred")
end try
Or, since the entire method is inside the TRY CATCH you can use the syntax you see where there is no TRY and ANY exception that is thrown by any line of code will jump to that single exception handler at the end as it the semantically the same as putting the entire body of the method in a try catch block
Var f As FolderItem = FolderItem.ShowSaveFileDialog(FileTypes1.Text, "Create Example.txt")
If f <> Nil Then
Var t As TextOutputStream = TextOutputStream.Create(f) // this line could raise an IOException.
t.WriteLine(TextField1.Value)
End If
Exception err As IOException
MsgBox("an IO exception occurred")
PERSONALLY I prefer to explcitily write the try catch
The difference is explained on the page for Exception.
The Exception statement catches runtime exceptions that occur anywhere within the method or event. In most cases using a Try...Catch is better since it allows you to catch exceptions in specific parts of your code.
The use of the IOException or RuntimeException keywords just has to do with what “type” of error is being thrown - which can be used with either the Exception only approach or with a Try...Catch statement.
The https://documentation.xojo.com/api/language/runtime.htmlException page has a complete list of the types of errors that can be raised.
I hope that helps.