# How to resolve type mismatch error in Gatling?
**URL:** https://community.gatling.io/t/how-to-resolve-type-mismatch-error-in-gatling/3403
**Category:** Gatling (Open-Source)
**Created:** [November 23, 2016, 11:26am UTC](https://community.gatling.io/t/how-to-resolve-type-mismatch-error-in-gatling/3403 "2016-11-23T11:26:42Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Peter](https://community.gatling.io/u/Peter)
#### Post date: [November 23, 2016, 11:26am UTC](https://community.gatling.io/t/how-to-resolve-type-mismatch-error-in-gatling/3403/1 "2016-11-23T11:26:42Z")
I am getting error while passing `session =>` in `.formParam` of **“Login” request**. Can anyone help? Thanks 🙂
Here is my script,
`
// Random user login logout
import scala.concurrent.duration.\_
import io.gatling.core.Predef.\_
import io.gatling.http.Predef.\_
import io.gatling.jdbc.Predef.\_
import io.gatling.core.validation.\_
class mamLoginLogout extends Simulation {
val testServerUrl = System.getProperty(“testServerUrl”, “[https://url](https://url)”)
val username = System.getProperty(“username”, “TestUser”)
val password = System.getProperty(“password”, “passwd”)
val userCount = Integer.getInteger(“userCount”, 10).toInt
val accountname = System.getProperty(“accountname”, “testrp”)
val endNum = Integer.getInteger(“EndNumber”, 10).toInt
val httpProtocol = http
.baseURL(testServerUrl)
val scn = scenario(“Login =\> Browse =\> Logout”)
.exec(http(“Login”)
.post("/ma/a/" + accountname + “/login”)
.headers(headers\_6)
.formParam(“username”, session =\> username + ThreadLocalRandom.current.nextInt(endNum))
.formParam(“password”, session =\> password)
// This script Runs perfact if I use below formParam (So its clear the problem is in above formParam with session =\>, I think it conflicts with below session which is used in .foreach())
//.formParam(“username”, username)
//.formParam(“password”, password)
)
.exec(http(“Browse”)
.get("/ma/assets/type=media%ofset=1%3Blimit=8")
.headers(headers\_12)
.check(jsonPath("$…keyframeId").findAll.saveAs(“IdList”))
)
.foreach("${IdList}", “id”) {
doIf(session =\> session(“id”).as[String] != “-1”)
{
exec(http(“Set\_Keyframes”)
.get("/ma/keyframes/${id};width=185;height=103")
)
}
}
.exec(http(“Logout”)
.get("/ma/logout")
.headers(headers\_80))
setUp(scn.inject(atOnceUsers(userCount))).protocols(httpProtocol)
}
`
**Fails at compile time, Here is the error:**
`
3674 [main] ERROR io.gatling.compiler.ZincCompiler$ - scala:68: type mismatch;
found : String("${IdList}")
required: ?{def apply: ?}
Note that implicit conversions are not applicable because they are ambiguous:
both method augmentString in object Predef of type (x: String)scala.collection.immutable.StringOps
and method stringToExpression in object Predef of type [T](string: String)(implicit evidence$1: scala.reflect.ClassTag[T])io.gatling.core.session.Expression[T]
are possible conversion functions from String("${IdList}") to ?{def apply: ?}
3674 [main] ERROR io.gatling.compiler.ZincCompiler$ - .foreach("${IdList}", “id”) {
3684 [main] ERROR io.gatling.compiler.ZincCompiler$ - ^
3695 [main] ERROR io.gatling.compiler.ZincCompiler$ - scala:68: type mismatch;
found : String(“id”)
required: ?{def apply: ?}
Note that implicit conversions are not applicable because they are ambiguous:
both method augmentString in object Predef of type (x: String)scala.collection.immutable.StringOps
and method stringToExpression in object Predef of type [T](string: String)(implicit evidence$1: scala.reflect.ClassTag[T])io.gatling.core.session.Expression[T]
are possible conversion functions from String(“id”) to ?{def apply: ?}
3695 [main] ERROR io.gatling.compiler.ZincCompiler$ - .foreach("${IdList}", “id”) {
3695 [main] ERROR io.gatling.compiler.ZincCompiler$ - ^
3994 [main] ERROR io.gatling.compiler.ZincCompiler$ - scala:53: not found: value ThreadLocalRandom
3995 [main] ERROR io.gatling.compiler.ZincCompiler$ - .formParam(“username”, session =\> username + ThreadLocalRandom.current.nextInt(endNum))
3995 [main] ERROR io.gatling.compiler.ZincCompiler$ - ^
4047 [main] ERROR io.gatling.compiler.ZincCompiler$ - three errors found
4048 [main] DEBUG io.gatling.compiler.ZincCompiler$ - Compilation failed (CompilerInterface)
`
Thanks.
---
### Author:  [@Peter](https://community.gatling.io/u/Peter)
#### Post date: [November 23, 2016, 1:21pm UTC](https://community.gatling.io/t/how-to-resolve-type-mismatch-error-in-gatling/3403/2 "2016-11-23T13:21:45Z")
Solved
I forgot to import this lib.
`import java.util.concurrent.ThreadLocalRandom`