Though the transaction class method is called on some ActiveRecord class, the objects within the transaction block need not all be instances of that class. This is because transactions are per-database connection, not per-model.
In this example a balance record is transactionally saved even though ...
Both #save and #destroy come wrapped in a transaction that ensures that whatever you do in validations or callbacks will happen under its protected cover. So you can use validations to check for values that the transaction depends on or you can raise exceptions in the callbacks to rollback, includin...
ActiveRecord::Base.transaction uses the ActiveRecord::Rollback exception to distinguish a deliberate rollback from other exceptional situations. Normally, raising an exception will cause the .transaction method to rollback the database transaction and pass on the exception. But if you raise an Activ...
class Animal
{
abstract int maxSize(); // must be implemented by sub-class
final float maxSizeInMeters() // can't be overridden by base class
{
return maxSize() / 100.0;
}
}
class Lion: Animal
{
override int maxSize() { return 350; }
}
void main()
{
...
C++11
The type_traits header contains a set of template classes and helpers to transform and check properties of types at compile-time.
These traits are typically used in templates to check for user errors, support generic programming, and allow for optimizations.
Most type traits are used to c...
Emacs uses the terms point, mark, and region to provide more precision about the selected text and position of the cursor. By understanding these terms, it'll help you understand and use other operations and functions.
The point is the place in a buffer where editing (i.e. insertion) is currently t...
Killing and yanking more or less correspond to what is usually called "cutting" and "pasting".
Killing
killing means deleting text, and copying it to the kill-ring (which could be seen as a sort of "clipboard" in the "cut & paste" terminology). The kill ...
Create a new Console Application
Add the NuGet package Microsoft.CodeAnalysis
Import the namespaces Microsoft.CodeAnalysis.MSBuild, System.Linq and Microsoft.CodeAnalysis.CSharp.Syntax
Write the following example code in the Main method:
// Declaring a variable with the current project file ...
Create a new console application with one line in the Main method: Console.WriteLine("Hello World")
Remember the path to the .csproj file and replace it in the example.
Create a new Console Application and install the Microsoft.CodeAnalysis NuGet package and try the following code:
cons...
Create a new console application with one line in the Main method: Console.WriteLine("Hello World")
Remember the path to the .vbproj file and replace it in the example.
Create a new Console Application and install the Microsoft.CodeAnalysis NuGet package and try the following code:
Cons...
In general, IBOutlets are used to connect an user interface object to another object, in this case a UIViewController. The connection serves to allow for the object to be affected my code or events programmatically. This can be done simply by using the assistant from a storyboard and control-clickin...
you can custom class below one
private final String PROTOCOL_CONTENT_TYPE = String.format("application/json; charset=%s", PROTOCOL_CHARSET);
public BooleanRequest(int method, String url, String requestBody, Response.Listener<Boolean> listener, Response.ErrorListener errorList...
Dynamic Arrays
Adding and reducing variables on an array dynamically is a huge advantage for when the information you are treating does not have a set number of variables.
Adding Values Dynamically
You can simply resize the Array with the ReDim Statement, this will resize the array but to if you ...
For a 12hour time format one can use:
^(?:0?[0-9]|1[0-2])[-:][0-5][0-9]\s*[ap]m$
Where
(?:0?[0-9]|1[0-2]) is the hour
[-:] is the separator, which can be adjusted to fit your need
[0-5][0-9] is the minute
\s*[ap]m followed any number of whitespace characters, and am or pm
If you need th...
Servant is a library for declaring APIs at the type-level and then:
write servers (this part of servant can be considered a web framework),
obtain client functions (in haskell),
generate client functions for other programming languages,
generate documentation for your web applications
and m...
In Tcl, a control structure is basically just another command. This is one possible implementation of a do ... while / do ... until control structure.
proc do {body keyword expression} {
uplevel 1 $body
switch $keyword {
while {uplevel 1 [list while $expression $body]}
u...
2.1.3
1. Preview Different Devices
There is a preview panel at the right of the android studio. In thispanel there is a button with device name with which you are previewing the UI of your app like this .
Click on small dropdown indicator of this and a floating panel will appear with all the pr...
