[Kotlin]Guard and If

👉🏻 스위프트의 Guard와 코틀린의 If를 비교하기 위한 설명입니다.
Here’s a comparison between Swift’s Guard and Kotlin’s If.

👉🏻 코틀린에는 Guard문법이 없습니다.
There is no guard syntax in Kotlin.

👉🏻 스위프트의 Guard문법과 IF가 어떻게 다른지 비교해 보세요
Compare how Guard and IF statements differ in Swift.

👉🏻 코틀린에서는 스위프트의 Guard를 다음과 같이 If문으로 표현할 수 있습니다.
In Kotlin, Swift’s Guard can be expressed as an If statement as follows:

        val v = value ?: return      // guard let
        if (v <= 0) return           // guard value > 0
        if (v == 999) return         // guard value != 999

👉🏻코드 / Code

package com.freelifemakers.guardif

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.layout.*
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Build
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import com.freelifemakers.guardif.ui.theme.GuardIfTheme

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            GuardIfTheme {
                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
                    ContentView(modifier = Modifier.padding(innerPadding))
                }
            }
        }
    }
}

@Composable
fun ContentView(modifier: Modifier = Modifier) {

    // SwiftUI의 @State
    var text by remember { mutableStateOf("") }

    // Swift guard 패턴 → Kotlin if + early return
    fun process(value: Int?) {
        val v = value ?: return      // guard let
        if (v <= 0) return           // guard value > 0
        if (v == 999) return         // guard value != 999

        println("Print Value: $v")
        text = "$v"
    }

    // 아래처럼 실행해도 동작합니다.
    // It also works if you run it like below.

    // process(1)

    // SwiftUI onAppear → Compose LaunchedEffect
    LaunchedEffect(Unit) {
        process(2)
    }

    // UI
    Column(
        modifier = modifier
            .fillMaxSize()
            .padding(16.dp),
        verticalArrangement = Arrangement.Center, // 수직 중앙 정렬 / vertical center alignment
        horizontalAlignment = Alignment.CenterHorizontally  // 수평 중앙 정렬 / horizontal center alignment
    ) {
        Icon(
            imageVector = Icons.Default.Build,
            contentDescription = "Globe"
        )
        Spacer(modifier = Modifier.height(16.dp))
        Text(text = "Text1: $text")
    }
}

@Preview(showBackground = true)
@Composable
fun ContentViewPreview() {
    GuardIfTheme {
        ContentView()
    }
}

👉🏻 스크린샷/ScreenShot