What is the best way to right the code? I have one...

# codingconventions

[KV]

What is the best way to right the code?
I have one variable like this ->

val filter: QueryFilter? = null

and I have one class like this ->

class QueryFilter(val by: String, val operator: String, val value: String)

And I am using the variable with class like this ->

filter.let {
                    mapOf(Pair("q[${<http://it.by|it.by>}_${it.operator}]", it.value))
                } ?: emptyMap()

But now I have a variable like this

val filter: Array<QueryFilter> = emptyArray()

then how to use the loop with filter function with the same class?
I want to know that is this the correct way to write a code ? or Is there any better way to write the below code?

filter.let { it ->
                    it.forEach {
                        mapOf(Pair("q[${<http://it.by|it.by>}_${it.operator}]", it.value))
                    }
                }
            }) as Map<String, String>

[Tobias Berger]

So first: your first filter property is nullable, so you probably meant to do ?.let.
The .let call in your last code snippet is obsolete, because you're only using it once to call forEach. Also, your forEach lambda shadows the it which makes code more confusing. Also the cast in the end wouldn't work, because forEach just returns Unit.

what you probably mean to do is this:

filter.associate { Pair("q[${<http://it.by|it.by>}_${it.operator}]", it.value) }

or to make it even a bit more "kotliny" but still doing exactly the same thing

filter.associate { "q[${<http://it.by|it.by>}_${it.operator}]" to it.value }

[KV]

@Tobias Berger So in the first part of code I am using the val filter: QueryFilter? = null because I know I have only QueryFilter data but now the requirement is we have to use ArrayOfQueryFilter with assigning the empty array val filter: Array<QueryFilter> = emptyArray().
So now I have to use forloop to get all the query filter data so I modified like below code (More readable format)

filter.let { it: Array<QueryFilter> ->
                    it.forEach {
                        mapOf(Pair("q[${<http://it.by|it.by>}_${it.operator}]", it.value))
                    }
                }
            }) as Map<String, String>

[KV]

Getting the error while removing the old code and using the new code which was shared by you

Type mismatch.
Required:
Map<String, String>
Found:
() → Map<String, String>

[Tobias Berger]

the for-loop creates some maps but doesn't do anything with them. The cast in the end will not work, because the forEach call (and the let call) returns Unit, not a map. Also, like I said, the let-call is obsolete if you only use the receiver once. It makes no difference if you do filter.let { it.forEach { ... } } or just filter.forEach { ... } and usually IntelliJ will actually tell you that.

The code I posted should produce a Map, not a lambda returning a map. can you show a more complete snippet of code that shows how you're using it?

[KV]

sealed class Api : JsonApi() {
    // API endpoints
    data class Index(val accountId: String, val filter: Array<QueryFilters> = emptyArray()) : Api()

    // JsonApi implementation
    override val baseUrl: String
        get() = "COMPANY URL"

    override val subpath: String
        get() = when (this) {
            is Index -> "data/$accountId/index"
        }

    override val method: HttpMethod
        get() = when (this) {
            is Index -> HttpMethod.Get
        }

    override val headers: Map<String, String>
        get() = emptyMap()

    override val queryParameters: Map<String, String>
        get() = when (this) {
            is Index -> ({
                filter.let { it ->
                    it.forEach {
                        mapOf(Pair("q[${<http://it.by|it.by>}_${it.operator}]", it.value))
                    }
                }
            }) as Map<String, String>
        }
}

class QueryFilters(val by: String, val operator: String, val value: String)

This queryParameters is a override method so adding the below part of code where we are creating the function and using the queryParameters with for loop line number 3.

1. private fun buildRequestUrl(): URL {
2.        val uriBuilder = Uri.parse(baseUrl).buildUpon()
3.        for ((key, value) in queryParameters) {
4.            uriBuilder.appendQueryParameter(key, value)
5.        }
6.        return URL(uriBuilder.build().toString())
7.    }

[Tobias Berger]

works fine if you use my code:

override val queryParameters: Map<String, String>
    get() = when (this) {
        is Index -> filter.associate { "q[${<http://it.by|it.by>}_${it.operator}]" to it.value }
    }

you probably tried this:

override val queryParameters: Map<String, String>
    get() = when (this) {
        is Index -> ({ filter.associate { "q[${<http://it.by|it.by>}_${it.operator}]" to it.value } })
    }

That wraps the code in a lambda body instead of calling it

[KV]

Thanks 🙂 for the help & your time to help me learn something new 🙂