How to extract a name of the class from its object?
For example I have a #list object which I know is surely an instance of List class. But how do I extract that directly in code?
This kind of information is rather basic Ruby programming. The answer is:
object.class
Extra tip for the next time: try finding this information yourself in the core library documentation. You know you have some kind of object, just start reading the documentation and you will find some method that suites your needs. Information about the methods you can perform on an object can be found here.
If you want to test for an instance of a specific class, I'd go with something like:
#list.is_a?(List)
Like Edwin said, object.class will give you the corresponding Class object. If you just want the name of the class, use object.class.name.
Related
I have a custom method in an ABAP class.
I used the 'Where used' tool to show where the class is called from but, as it turns out, it's called from somewhere else I didn't expect.
So what's the best way of showing a complete list of everything that calls the method?
Due to the wonders of object-oriented programming, an instance of a class can hide behind a reference to one of its base classes or interfaces it implements. For example:
DATA foo TYPE REF TO z_my_interface.
CREATE OBJECT foo TYPE z_my_class.
" lots of more code
foo->bar( ).
You can not find this reference to z_my_class->foo with its "Where Used" list, because at that code location foo could also be a reference to an instance of any other class which implements z_my_interface. But you might be able to find this if you don't just look at the where-used list of the method but at the where-used list of the whole class or the interface / base class which declares the method.
And then there are evil dynamic programming tricks like this which determine methods and classes at runtime:
DATA foo TYPE REF TO object.
CONSTANTS: classname TYPE string VALUE 'Z_MY_CLASS',
methodname TYPE string VALUE 'BAR'.
CREATE OBJECT foo TYPE (classname).
CALL METHOD foo->(methodname).
There is no chance to find this with the where-used tool. But if the class- and/or method name does actually appear in the code (it might not, for example if they are read from a customizing table) then you can use the report RS_ABAP_SOURCE_SCAN. This handy little tool allows you to select a set of ABAP programs and search for strings (and even regular expressions) within their sourcecodes.
However, if you know the method gets called when you do something specific as a user and just want to know where, then it can be easier to just set a debugger breakpoint in the method, run into it and check the call stack.
Sorted using the code_scanner transaction.
I have been working on implementing my own ORM. And I was wondering how the rails path helper extracts the ID from the object. For example how would I make this work for my ORM?
#contact = Contact.first
contact_path(#contact)
Any help would be greatly appreciated!
Update:
My object does have an ID attribute and responds to it. But yet the path helper returns an error.
In a nutshell you want to be activemodel compliant. This will make url helpers, form_for(#contact) and so on work.
You also get to (optionally) use a bunch of modules dealing with
things such as validations, dirty attributes etc.
There are only a handful of methods you have to implement. There's also an
ActiveModel::Lint module that tests that your implementations of these
primitives are valid, and which also serves as documentation. In particular you need to implement to_param and persisted?. I think some of the naming stuff only gets used if you do stuff like link_to 'foo', #contact
The method checks to see if you've passed it an object, or an integer. If it's an object and that object has an id method (respond_to?(:id)), it uses its ID. Pretty dead simple.
I'm working on transforming legacy code to a new one in a new project.
There are more than 100 of similar codes and I have to transform them to a slightly different new format.
Basically, get a particular method from the legacy application, rename it, modify the content of the method to fit the new format, and put that method in a class for the new project.
Since there are more than 100 of them, I want to do it programmatically, instead of manually copying and pasting and modifying.
Is there a way to get the source code of a method as a string dynamically?
It must be only for a specific method, not the entire content of the class or file.
After that is done, I think I can just do gsub, or maybe use AST (Abstract Syntax Tree) to pass to Ruby2Ruby.
So I need more than the answers for the question How can I get source code of a methods dynamically and also which file is this method locate in?.
Any help will be greatly appreciated.
After further investigation, I resorted to use live_ast gem to convert the method object to Abstract Syntax Tree and generate the code for the method from that Abstract Syntax Tree (it's using Ruby2Ruby underneath).
Actually, live_ast provides a convenient method to_ruby to do the both steps.
It's working very well.
e.g.
require 'live_ast'
require 'live_ast/to_ruby'
SomeClassWithMethod.instance_method(:method_name).to_ruby
You could use source_location to find the beginning of the method you're looking for, then parse the file from that point until the end of the method. You could examine each line of the file starting from the start of the method, incrementing a counter when you find the start of a block and decrementing it when you reach the end of a block, until the counter reaches 0.
Anyone know how to get the sender class/module in ruby?
caller[0] is helpful to derive the filename and linenumber sending.
But knowing the class would be helpful. Can't find it any searches?
This would be impossible. You shouldn't be specialising your behaviour in a method based on the calling class anyway.
Think about it this way - the caller could be an anonymous function (proc) created in one class, then given to another one and invoked from a third place. You wouldn't get anything useful.
Instead, I'd look at what you're trying to achieve here, and think of another way to get there! :)
Check out this gem: https://github.com/asher-/sender
I would like to check if my assumption about codeigniter is right ?
We would normally extend a class when we are trying to include more functionality to the core, such as MY_Controller extends Controller, MY_Model extends Model etc...
But for example, if we are in the checkout library retrieving some checkout info(eg, product_id), we can just $this->load->library('product_lib',array('product_id'=>$product_id)) and we can easily $this->product_lib->product_name etc... from the checkout library right?
The $this->load thing is kind of equivalent to "hard code" checkout library to extend product_lib(class checkout_lib extends product_lib) to be able to use whatever methods/variables there is in the product_lib.
Please enlighten me.
In CodeIgniter $this->load is like having a resource manager (e.g. resourceManager->load("path/to/file")) and it takes care of loading the library, and passing any arguments you specify and such, easily allowing you to quickly get to using it.
So if you have a variable named product_name in your product_lib then yes calling $this->product_lib->product_name will be accessing that variable.
Really it just places the library into an array with the library name as the key and the instance of the library as the value so calling $this->product_lib is really calling something similar to $loadedLibraries['product_lib'] and returning the instance.
I hope that answers what you are asking, I'm quite tired and could have miss understood you question.
I think you misunderstood the OO paradigm and the way CI work.
$this->load is same with instantiate an object of the library/model, or load the helper file. CI have some sort of management to see if the helper/library/model already uploaded or not.
In other hand, the extends is used when defining a class, to tell PHP that the class will be inherit the parent class properties and method. A class is a blue print of object it will produce.
Maybe you can start by understanding the OO concept first. You can read this as a start, and see the reference used there.