Nested Containers

Nested Containers 🗄

Last time we used Nested Arrays to store classes, now we are going to do the same thing with Nested Containers witch are containers inside another containers.

The declare() method 📌

We use the declare() method to create arrays, containers and nested containers.

• Creating a container

    // Structure
    database.declare("container_name", lan::Container);
    // Example - Creating "colors"
    database.declare("colors", lan::Container);

• Creating a nested container

    // Structure
    database.declare("container_name", "nested_container_name", lan::Container);
    // Example - Creating a "colors.red"
    database.declare("colors", "red", lan::Container);

The Anchor aka "@" again 😅

As we saw in the Nested Arrays's chapter, anchors are a good way to avoid big and confusing addresses. This time we are going to use them again, in Containers to avoid addresses like home.people.Muala.pets.cat every time that i need get my little cat's name!

The set_anchor() method in Nested Containers 🙃

    // Usage
    database.set_anchor("container_address");
    // Example - Setting the anchor to "home.cats"
    database.set_anchor("home.cats");

The set() method for the last time! 😄

To set variables inside of Nested Containers we also use the set() method

    // Usage
    database.set<data_type>("container_address", "variable_name", variable_data, landb_type);
    // Example - Setting food.fruits.favourite
    database.set< std::string >("food.fruits", "favourite", "Mango", lan::String);

Declaring a Nested Container 🗳

(Example program to recreate the first class of our classes example from Nested Arrays)

First we create the container to store our classes

    // Creating the classes container
    database.declare("classes", lan::Container);

Then we create the nested container to store the class_a

    // Creating a classes.class_a nested container
    database.declare("classes", "class_a", lan::Container);

Now it's time to add student_1 .

    // Creating the first student's container
    database.declare("classes.class_a", "student_1", lan::Container);

Here we set the anchor to "classes.class_1.student_1" because we are going to use that address many times to set the first student's data

    // Setting the anchor to reuse the address "classes.class_a.student_1"
    database.set_anchor("classes.class_a.student_1");

Adding the first student's data in "@", with is a synonym to "classes.class_a.student_1"

    // Adding student_1.name
    database.set< std::string >("@", "name", "Anita", lan::String);
    
    // Adding student_1.average
    database.set< float >("@", "average", 16, lan::Float);
    
    // Adding student_1.has_passed
    database.set< bool >("@", "has_passed", true, lan::Bool);

Setting the 2nd and 3rd students' data

    // Second student
    
    // Creating the second student's container
    database.declare("classes.class_a", "student_2", lan::Container);
    
    // Setting the anchor to reuse the address "classes.class_a.student_2"
    database.set_anchor("classes.class_a.student_2");
    
    // Adding student_2.name
    database.set< std::string >("@", "name", "Carlos", lan::String);
    
    // Adding student_2.average
    database.set< float >("@", "average", 12, lan::Float);
    
    // Adding student_2.has_passed
    database.set< bool >("@", "has_passed", true, lan::Bool);
    
    // Third student
    
    // Creating the third student's container
    database.declare("classes.class_a", "student_3", lan::Container);
    
    // Setting the anchor to reuse the address "classes.class_a.student_3"
    database.set_anchor("classes.class_a.student_3");
    
    // Adding student_3.name
    database.set< std::string >("@", "name", "Zinha", lan::String);
    
    // Adding student_3.average
    database.set< float >("@", "average", 8, lan::Float);
    
    // Adding student_3.has_passed
    database.set< bool >("@", "has_passed", false, lan::Bool);
    

Printing the Nested Array data 📺

    // Printing everything
    for (int i = 0 ; i < 3 ; i++ ){
        // setting anchor to classes.class_a.student_i
        database.set_anchor("classes.class_a.student_"+std::to_string(i+1));
        
        std::cout << "Name: " << database.get< std::string >("@", "name", lan::String) << " - "
        << "Average: " << database.get< float >("@", "average", lan::Float) << " - "
        << "Passed: " << database.get< bool >("@", "has_passed", lan::Bool) << std::endl;
    }
    
    return 0;
}

Here is the entire code {✨}

#include <iostream>
#include "landb.hpp"

int main(int argc, const char * argv[]) {
    
    // Database
    lan::db database;
        
    // Creating the classes container
    database.declare("classes", lan::Container);
    
    // Creating a classes.class_a nested container
    database.declare("classes", "class_a", lan::Container);
    
    // Creating the first student's container
    database.declare("classes.class_a", "student_1", lan::Container);
    
    // Setting the anchor to reuse the address "classes.class_a.student_1"
    database.set_anchor("classes.class_a.student_1");
    
    // Adding student_1.name
    database.set< std::string >("@", "name", "Anita", lan::String);
    
    // Adding student_1.average
    database.set< float >("@", "average", 16, lan::Float);
    
    // Adding student_1.has_passed
    database.set< bool >("@", "has_passed", true, lan::Bool);

    // Second student
    
    // Creating the second student's container
    database.declare("classes.class_a", "student_2", lan::Container);
    
    // Setting the anchor to reuse the address "classes.class_a.student_2"
    database.set_anchor("classes.class_a.student_2");
    
    // Adding student_2.name
    database.set< std::string >("@", "name", "Carlos", lan::String);
    
    // Adding student_2.average
    database.set< float >("@", "average", 12, lan::Float);
    
    // Adding student_2.has_passed
    database.set< bool >("@", "has_passed", true, lan::Bool);
    
    // Third student
    
    // Creating the third student's container
    database.declare("classes.class_a", "student_3", lan::Container);
    
    // Setting the anchor to reuse the address "classes.class_a.student_3"
    database.set_anchor("classes.class_a.student_3");
    
    // Adding student_3.name
    database.set< std::string >("@", "name", "Zinha", lan::String);
    
    // Adding student_3.average
    database.set< float >("@", "average", 8, lan::Float);
    
    // Adding student_3.has_passed
    database.set< bool >("@", "has_passed", false, lan::Bool);
    
    // Printing everything
    for (int i = 0 ; i < 3 ; i++ ){
        // setting anchor to classes.class_a.student_i
        database.set_anchor("classes.class_a.student_"+std::to_string(i+1));
        
        std::cout << "Name: " << database.get< std::string >("@", "name", lan::String) << " - "
        << "Average: " << database.get< float >("@", "average", lan::Float) << " - "
        << "Passed: " << database.get< bool >("@", "has_passed", lan::Bool) << std::endl;
    }
    
    return 0;
}

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