͔Θ͍͍খௗΛғ͏
 ͓ͬ͞Μୡͷ࿩ Mercari, Inc 

About me Jun Sugai @calciolife Mercari
 

Agenda • Welcome Kotlin • Kotlinizing • using Kotlin 

Welcome 

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Ͳ͏͍͏ܦҢͰ? Welcome Kotlin/Kotlin ಋೖ 

ָͦ͠͏ͳงғؾ͋ͬͨ Welcome Kotlin/Kotlin ಋೖ 

•ָͦ͠͏ͳΒ΍ͬͯ͠·͏ •໘നͦ͏ͳ΍ͬͯ͠·͏ •໰୊͕ͳ͚Ε͹ڋ൱͠ͳ͍ Welcome Kotlin/Kotlin ಋೖ 

Kotlinizing 

•ςετίʔυ •Өڹͷগͳ͍ͱ͜Ζ͔Β •৽نͷػೳ͔Β •etc... ABC 

•ςετίʔυ •Өڹͷগͳ͍ͱ͜Ζ͔Β •৽نͷػೳ͔Β •etc... ABC શ෦Ͱ͢ΑͶ 

ಋೖ͸࢖ͬͯײ૝Λॻ͘·Ͱ΍Δ ݁ՌΛग़ͯͦ͜͠੒Ռ ΠλϦΞ୅දͩͬͯϘίϘί 

using Kotlin 

είʔϓؔ਺ Kotlin ͕Α΄Ͳಛघͳ࣮૷/࠷దԽͰ ͳ͍ݶΓ͸είʔϓؔ਺͸ཁ͢Δʹ ϝιουΛ࡞ͬͯॲཧΛҠ͔͑͠Δ ίʔυʹࠩ͠ସ͑Δ
 

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είʔϓؔ਺ ࢖͏΂͖ɻReadable ͬͯେࣄɻ 

var/val/collection ΞΫηε੍ޚ΍ΧϓηϧԽͳͲ͸ Java ΑΓ΋෼͔Γ΍͍͢൓໘ɺ
 ଟ༻͠΍͢͞͸Ͳ͏ͳΜͩΖ͏? 

var/val/collection public class SearchListAdapter extends RecyclerView.Adapter { private val List dataSet = new ArrayList<>(); public SearchListAdapter(SearchListener listener) { this.listener = listener; } //... @Override public int getItemCount() { return dataSet.size(); } public void setDataSet(List dataSet) { this.dataSet = dataSet; notifyDataSetChanged(); } 

var/val/collection public class SearchListAdapter extends RecyclerView.Adapter { private val List dataSet = new ArrayList() //େࣄͳͱ͜Ζ͚ͩ public void setDataSet(List dataSet) { this.dataSet.clear() this.dataSet.addAll(dataSet) notifyDataSetChanged(); } // Kotlin ͩͱ immutable ʹͨ͘͠ͳͬͪΌ͏ 

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var/val/collection private val List dataSet = new ArrayList() //େࣄͳͱ͜Ζ͚ͩ public void setDataSet(List dataSet) { this.dataSet.clear() this.dataSet.addAll(dataSet) notifyDataSetChanged(); } •clear() -> addAll() ͷྲྀΕ͸ GC ίετతʹͲ͏ͳͷ? •addAll() Ͱ௥Ճ͢Δࡍͷཁૉ͕ڊେͳ instance ΍ڊେͳ heap ΁ͷࢀরΛอ࣋͢Δߏ଄ͩͱ
 clear() -> adAll() ͚ͩͰ GC ͕૸ΔՄೳੑ͸? •ཁૉͷίϐʔΛ࡞Δ heap ίετ/ϑοτϓϦϯτ͸ॲཧશମͰແࢹͰ͖Δ΄Ͳখ͍͞? 

var/val έʔεʹԠͯ͡ Readable ͳͷ͸େࣄ͚ͩͲϦιʔε͸༗ݶɻ ύϑΥʔϚϯε͸ "ίʔυͷ඼࣭" Ͱ͸ͳ͘
 "ΞϓϦͷ඼࣭" ͳͷͰಉ͡؍఺Ͱٞ࿦͠ͳ͍ɻ 

ଞͷࣄྫ͸ɺ·ͨผͷػձʹ! ৘ใަ׵ͱ͔͍ͯͩ͘͠͞