Software And Architecture

Introduction Sequences in Kotlin are similar to that of the stream s in Java, where in the evaluation happens lazily and the volume of data processed in each step in the chain are reducing based on the met criteria. Sample Let us consider the below given sample data class data class Car ( val model : String , val year : Int ) We can create a collection of cars so that we can evaluate both and understand the difference between collections and sequence   in Kotlin var cars = listOf ( Car ( "Toyota" , 2021), Car ( model = "Tesla-S" , 2022), Car ( "Mercedes - Maybach" , 2022) ) Sequence In the below given snippet of code, we are performing the filtering of cars by name and then printing the year println ( cars . asSequence (). filter { it . model == "Toyota" } . map { it . year } This produces the output as given below kotlin.sequences.TransformingSequence@b97c004a This is because the sequence is lazy and is not evaluated as there is

Introduction This is a process in which we can be able to extract properties of interest from an object  / collection. We have been used to using destructuring in javascript and other functional languages whereas in Java / C# we have not been able to do this. However, kotlin has added the functionality to destructure classes by properties, collections, maps etc. Destructuring classes To enable a class to be destructured, should we do anything in kotlin? The answer is yes and no.. looks puzzling ain't it. Destructuring a class Below is a regular class (non data class) which needs implementation to allow it to be destructured class User ( var mail : String , var deptId : Long ) { operator fun component1 () = mail operator fun component2 () = deptId } Destructuring a data class Below is a declaration of a data class which comes with the support for destructuring for free as like toString, hashcode etc.. data class CompanyUser ( var mail : String , var deptId : Long ) Now that

Collections This post provides some of the operations that can be done in the collections using kotlin The below is the base type definitions that will be used in the below collection queries data class Shop ( val name : String , val customers : List < Customer >) data class Customer ( val name : String , val city : City , val orders : List < Order >) { override fun toString () = " $ name from ${ city . name } " } data class Order ( val products : List < Product >, val isDelivered : Boolean ) data class Product ( val name : String , val price : Double ) { override fun toString () = "' $ name ' for $ price " } data class City ( val name : String ) { override fun toString () = name } Operations on collections // Return a list of customers, sorted in the descending by number of orders they have made fun Shop. getCustomersSortedByOrders (): List<Customer> = this .customers.sortedByDescending( { it -> it.order

The Problem This is a very short post on how to be very careful when converting a collection (array) of strings to integers Let us assume that we receive from an API call or from some other source a collection of numbers in string format Example ["1","9","2"] In this case we might be planning to use the map function along with the parseInt to get the job done as given below ["1","9","2"].map(parseInt) However, the catch here is that the above method will return the below response (3) [1, NaN, NaN] This will be a lot confusing to many because the first number gets parsed and the remaining ones does not. Let us consider another example ["10","10","10","10"].map(parseInt) This results in a similar output where the developer might get even puzzled [10, NaN, 2, 3] This looks like the last 2 numbers are getting printed like their i