Ruby with Qt

qtruby

I'm working on a multi form Ruby-Qt program using, and I'm having a problem with controlling secondary windows from the primary one.
How can i disable the primary window when any secondary one is open, also how to take a secondary window output to use it on the primary one, and finally, sorry this is a silly one, what is the appropriate method for closing any window (like this.close in .net) ????

Best Solution

You can make a dialog modal, this disables user interaction with other windows of your application until the user closes the modal window. Use Qt::Dialog.exec instead of Qt::Dialog.show to pop up the window as a modal dialog. This method returns Qt::Dialog::Accepted or Qt::Dialog::Rejected depending on how the user closed the dialog.

To use data from a dialog in the main application window, just save the data somewhere in the dialog class where the main program can access it. For example:

class MyDialog < Qt::Dialog
    attr_reader :data
[...]
    def updateData(new)
        @data = new
    end
end

dlg = MyDialog.new(self)
if (dlg.exec == Qt::Dialog::Accepted)
    @aButton.text = dlg.data
end

If you are using a dialog, you need to exit it with accept() or reject(), in most cases these are connected to the OK and Cancel button:

connect(okButton, SIGNAL('clicked()'), self, SLOT('accept()'))
connect(cancelButton, SIGNAL('clicked()'), self, SLOT('reject()'))

Other windows can be closed with the close() method.

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Ruby – How to call shell commands from Ruby

This explanation is based on a commented Ruby script from a friend of mine. If you want to improve the script, feel free to update it at the link.

First, note that when Ruby calls out to a shell, it typically calls /bin/sh, not Bash. Some Bash syntax is not supported by /bin/sh on all systems.

Here are ways to execute a shell script:

cmd = "echo 'hi'" # Sample string that can be used

Kernel#` , commonly called backticks – `cmd`

This is like many other languages, including Bash, PHP, and Perl.

Returns the result (i.e. standard output) of the shell command.

Docs: http://ruby-doc.org/core/Kernel.html#method-i-60
```
value = `echo 'hi'`
value = `#{cmd}`
```
Built-in syntax, %x( cmd )

Following the x character is a delimiter, which can be any character. If the delimiter is one of the characters (, [, {, or <, the literal consists of the characters up to the matching closing delimiter, taking account of nested delimiter pairs. For all other delimiters, the literal comprises the characters up to the next occurrence of the delimiter character. String interpolation #{ ... } is allowed.

Returns the result (i.e. standard output) of the shell command, just like the backticks.

Docs: https://docs.ruby-lang.org/en/master/syntax/literals_rdoc.html#label-Percent+Strings
```
value = %x( echo 'hi' )
value = %x[ #{cmd} ]
```
Kernel#system

Executes the given command in a subshell.

Returns true if the command was found and run successfully, false otherwise.

Docs: http://ruby-doc.org/core/Kernel.html#method-i-system
```
wasGood = system( "echo 'hi'" )
wasGood = system( cmd )
```
Kernel#exec

Replaces the current process by running the given external command.

Returns none, the current process is replaced and never continues.

Docs: http://ruby-doc.org/core/Kernel.html#method-i-exec
```
exec( "echo 'hi'" )
exec( cmd ) # Note: this will never be reached because of the line above
```

Here's some extra advice: $?, which is the same as $CHILD_STATUS, accesses the status of the last system executed command if you use the backticks, system() or %x{}. You can then access the exitstatus and pid properties:

$?.exitstatus

For more reading see:

Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

.nil? can be used on any object and is true if the object is nil.

.empty? can be used on strings, arrays and hashes and returns true if:

String length == 0
Array length == 0
Hash length == 0

Running .empty? on something that is nil will throw a NoMethodError.

That is where .blank? comes in. It is implemented by Rails and will operate on any object as well as work like .empty? on strings, arrays and hashes.

nil.blank? == true
false.blank? == true
[].blank? == true
{}.blank? == true
"".blank? == true
5.blank? == false
0.blank? == false

.blank? also evaluates true on strings which are non-empty but contain only whitespace:

"  ".blank? == true
"  ".empty? == false

Rails also provides .present?, which returns the negation of .blank?.

Array gotcha: blank? will return false even if all elements of an array are blank. To determine blankness in this case, use all? with blank?, for example:

[ nil, '' ].blank? == false
[ nil, '' ].all? &:blank? == true

Best Solution

Related Solutions

Ruby – How to call shell commands from Ruby

Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

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