giritharan
Mon May 20 2024
There are two ways to call respond_to: Either we can pass it as a list of symbols or pass a block Block Version:
def index
@people = Person.all
respond_to do |format|
format.json { render json: @people}
format.xml { render xml: @people }
format.html { render :index}
end
end
Symbol version:
def index
@people = Person.all
respond_to :json, :xml, :html
end
#respondto #actionview #rails
soniya.rayabagi
Mon May 20 2024
kubectl rollout restart deployment <deployment-name>
command used to restart pods managed by a Kubernetes deployment without making any modifications to the deployment configuration.
#devops #Kubernetes #rollingrestart
syedsibtain
Mon May 13 2024
Active Record is the Object-Relational Mapping (ORM) layer provided by Ruby on Rails. It facilitates the interaction between Ruby objects and a relational database. It helps us interact with our database using Ruby instead of writing SQL queries directly.
Key features of ActiveRecord include:
• Model Definition: ActiveRecord allows developers to define models that represent database tables. These models inherit from the ActiveRecord::Base class and include methods for defining associations, validations, and callbacks.
• CRUD Operations: ActiveRecord provides methods for performing CRUD (Create, Read, Update, Delete) operations on database records. These methods allow developers to manipulate records using Ruby syntax without writing explicit SQL queries.
• Associations: ActiveRecord simplifies the definition and management of associations between models. It supports various types of associations, including belongs_to, has_many, has_one,
and has_and_belongs_to_many,
allowing us to express complex relationships between database tables.
• Validations: ActiveRecord includes a robust validation framework for ensuring data integrity. We can define validation rules such as presence, uniqueness, length, format, and custom validations to enforce data constraints at the model level.
#orm #rails
giritharan
Mon May 13 2024
What is happening behind the scenes after we configured database credentials in database.yml
• Conduct the three-way handshake
to establish a TCP connection to the server.
• Exchange preferences and requirements with the database software to establish the session parameters.
• Perform database authentication
checks to establish the client's identity.
• PostgreSQL supports several authentication methods, such as passwords (plaintext or MD5),GSSAPI, SSPI, and more.
• The client (Rails, via ActiveRecord) can now send commands to the server. Commands are typically SQL statements. These statements are sent as simple text strings in the 'Query' message format.
How Number of connection affects the database server
• When the number of connections or pools to a server increases, CPU usage will rise. This increased demand for memory and CPU resources can affect other operations, such as transaction speeds. Managing many connections can also reduce the effectiveness of the database and decreasing overall system performance.
What will happen if we give more connections then we configured in PSQL?
• When that limit of a db is reached, additional connection requests are rejected.
How connections b/w rails and PSQL established and maintained?
• Connection pooling
is a technique where database connections are reused for multiple requests instead of being closed after each query. This approach uses a connection pooler
, a software that manages the connections between the database and its client applications, optimizing the use of resources and improving performance.
• Establishing the connections is a fairly long operation.
• Connection pooler
is sitting b/w client and server. client connects to the connection pooler instead of directly to the database. Req is sent to pooler and the pooler interprets queries returns back the response from DB.
• Once the response is returned it closes the connection. But the thing here is opening and closing connection is not overhead comparatively with client and DB connections.
#orm #activerecord #psql #rails
giritharan
Fri May 10 2024
Dup vs clone while dealing with Active Record:
• Dup creates a new record with a blank ID, which will create a new object on the database with a new ID after hitting .save
.
user = User.first
user1 = user.dup
user1:
<User id: nil, name: "Rails">
• clone creates a new record with the same ID, after hitting save on the clone object this will overwrite the existing data.
user = User.first
user1 = user.clone
<User id: 1, name: "Rails">
• If you change some value on the above attribute and put .save
it will overwrite the original obj.
#dupvsclone #ruby #rails
syedsibtain
Thu May 09 2024
In Rails, the resources
method provides a convenient way to define RESTful routes for our application's resources. Instead of manually specifying separate routes for each CRUD action (Create, Read, Update, Delete), we can use the resources
method to define all these routes with a single line of code.
# config/routes.rb
Rails.application.routes.draw do
resources :students
end
With this single line of code, Rails automatically generates the following RESTful routes for the students
resource:
GET /students # Index action (display a list of students)
GET /students/new # New action (display a form to create a new student)
POST /students # Create action (create a new student)
GET /students/:id # Show action (display details of a specific student)
GET /students/:id/edit # Edit action (display a form to edit a specific student)
PATCH /students/:id # Update action (update a specific student)
PUT /students/:id # Update action (update a specific student)
DELETE /students/:id # Destroy action (delete a specific student)
#rails #routes
syedsibtain
Thu May 09 2024
In a Rails application, the seeds.rb
file is used to populate the database with initial data. This file typically resides in the db
directory of our Rails application. The data added through the seeds.rb
file is often used for testing or for providing initial data in a fresh installation of the application.
After defining the data in the seeds.rb
file, we can populate the database by running the rails db:seed
#rails #database
giritharan
Wed May 08 2024
Generic Classes:
• To ensure that the function correctly infers the type of the argument passed to it and returns the same type, you can use TypeScript's generic type notation
function identityType<Type>(prop: Type): Type {
return prop;
}
identityType(1);
• If we plan to use generic <>
have to add, it tells ts compiler as the function in generic fn.
• From the above code we can see the example, if we planned to use string we can or boolean we can. The thing is both prop and return type has to be similar
#typescript #javascript
giritharan
Wed May 08 2024
Difference between any
and unkown
type in ts
any:
- The
any
type is a dynamic type, variables of typeany
can hold values of any data type, and TypeScript type checking is effectively turned off for them. - While
any
provides flexibility, it bypasses TypeScript's type checking entirely, which can lead to loss of type safety and potentially introduce bugs.
unknown:
- The
unknown
type is a type-safe counterpart ofany
. It represents values of an unknown type. - Variables of type
unknown
can hold values of any type, butyou cannot perform operations
on them without first narrowing their type or asserting a more specific type.
Both any
and unknown
provide flexibility in handling values of unknown types, any
completely disables type checking, while unknown
enforces type safety by requiring you to explicitly narrow the type before performing operations on the value. It's generally recommended to prefer unknown
over any
when dealing with values of unknown types, as it helps maintain type safety in your TypeScript code.
#typescipt #javascipt
giritharan
Wed May 08 2024
Classes And Functions in Ts. Classes: • Ts add helps to add type annotations for the classes.
class User {
constructor(public name: string, public age: number) {}
}
const ue = new User("github", 24);
• In Ts we don't need to initialize the properties and values inside the constructor if we are using access modifiers in the params. TypeScript will automatically initialise and assign values to class properties.
Getters / Setters:
• Classes can also have accessors
• For the getter function we can able to set return value type but for setter function we can't.
• setter functions are always expected props.
• If a getter exists but no setter the property is automatically readonly
• If the type of the setter parameter is not specified, it is inferred from the return type of the getter
• For class props always try to use _
name convention for better maintainbility.
class User {
private _currentCount: number = 0;
constructor(public name: string, public age: number) {}
get fetch_name(): string {
return this._name;
}
get fetchCount(): number {
return this._currentCount;
}
set increaseCount(prop: number) {
this._currentCount = prop + this._currentCount;
this.logData();
}
private logData(): void {
console.log("Count Increased");
}
}
const fetchUser = new User("github", 24);
Abstract:
• If classes or method
are marked as abstract those are only for readonly purposes, means they can be only used as base class/sub class.
• So that reason we can't create object on the class who are marked as abstract
.
abstract class Photo {
constructor(public isCameraOn: boolean, public isFlashOn: boolean) {}
}
class Phone extends Photo {}
const ph = new Phone(true, true);
#typescript #javascript
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