EngineerX.go#2 - A Tour of Goで一緒にGo入門 : メソッドとインタフェース編 -

A T O U R O F G O Ұ
ॹ ʹ ( 0 ͷ ੈ ք Λ ๯ ݥ ͠ Α ͏ ʂ EngineerX.go #2 5IF(PQIFSDIBSBDUFSJTCBTFEPOUIF(PNBTDPUEFTJHOFECZ3FOÉF'SFODI

GoͬͯͲΜͳݴޠʁ

ABOUT GO Go͸ɺγϯϓϧͰ৴པੑͷߴ͍ޮ཰తͳιϑτ΢ΣΞΛ ؆୯ʹߏஙͰ͖ΔΦʔϓϯιʔεͷϓϩάϥϛϯάݴޠͰ͢ɻ (By https://golang.org/)

GoͷੈքΛཱྀ͠Α͏ʂ A TOUR OF GO

• جຊߏจ – ύοέʔδɺม਺ɺؔ਺ – ੍ޚจɿGPS JG FMTF TXJUDI EFGFS
– ͦͷଞͷܕɿTUSVDU TMJDFT NBQT • ϝιουͱΠϯλϑΣʔε – ϝιουͱΠϯλϑΣʔε • ฒߦੑ – ฒߦੑ A TOUR OF GO ҰॹʹGOͷੈքΛ๯ݥ͠Α͏ʂ "5PVSPG(Pͷߏ੒

– ͦͷଞͷܕɿTUSVDU TMJDFT NBQT • ϝιουͱΠϯλϑΣʔε – ϝιουͱΠϯλϑΣʔε • ฒߦੑ – ฒߦੑ A TOUR OF GO ҰॹʹGOͷੈքΛ๯ݥ͠Α͏ʂ લ ճ · Ͱ ͷ ൣ ғ "5PVSPG(Pͷߏ੒

– ͦͷଞͷܕɿTUSVDU TMJDFT NBQT • ϝιουͱΠϯλϑΣʔε – ϝιουͱΠϯλϑΣʔε • ฒߦੑ – ฒߦੑ A TOUR OF GO ҰॹʹGOͷੈքΛ๯ݥ͠Α͏ʂ ຊ ೔ ͷ ൣ ғ "5PVSPG(Pͷߏ੒

લճ·Ͱͷ෮श ˍ ࣭໰λΠϜ

1BDLBHF WBSJBCMFT BOEGVODUJPOT 1BDLBHFT *NQPSUT &YQPSUFEOBNFT 'VODUJPOT 'VODUJPOTDPOUJOVFE .VMUJQMFSFTVMUT /BNFESFUVSOWBMVFT
7BSJBCMFT 7BSJBCMFTXJUIJOJUJBMJ[FST 4IPSUWBSJBCMFEFDMBSBUJPOT #BTJDUZQFT ;FSPWBMVFT 5ZQFDPOWFSTJPOT 5ZQFJOGFSFODF $POTUBOUT /VNFSJD$POTUBOT લճ·Ͱͷൣғ Gopher Artwork by Ashley McNamara

'MPXDPOUSPMTUBUFNFOUT GPS JG FMTF TXJUDIBOEEFGFS 'PS 'PSDPOUJOVFE 'PSJT(P`TlXIJMFz 'PSFWFS *G
*GXJUIBTIPSUTUBUFNFOU *GBOEFMTF 4XJUDI 4XJUDIFWBMVBUJPOPSEFS 4XJUDIXJUIOPDPOEJUJPO %FGFS 4UBDLJOHEFGFST લճ·Ͱͷൣғ Gopher Artwork by Ashley McNamara

.PSFUZQFT TUSVDUT TMJDFT BOENBQT 1PJOUFST 4USVDUT 4USVDU'JFMET 1PJOUFSTUPTUSVDUT 4USVDU-JUFSBMT "SSBZT
4MJDFT 4MJDFTBSFMJLFSFGFSFODFTUPBSSBZT 4MJDFTMJUFSBMT 4MJDFTEFGBVMUT 4MJDFTMFOHUI /JMTMJDFT $SFBUJOHBTMJDFXJUINBLF 4MJDFTPGTMJDFT "QQFOEJOHUPBTMJDF 3BOHF 3BOHFDPOUJOVFE .BQT .BQMJUFSBMT .BQMJUFSBMTDPOUJOVFE .VUBUJOH.BQT 'VODUJPOWBMVFT 'VODUJPODMPTVSFT લճ·Ͱͷൣғ Gopher Artwork by Ashley McNamara

休憩タイム

ϝιουͱΠϯλϑΣʔε   

METHODS ܕʹϝιου NFUIPE Λ ఆٛ͢Δ͜ͱ͕Ͱ͖Δ

METHODS ܕʹϝιου NFUIPE Λ ఆٛ͢Δ͜ͱ͕Ͱ͖Δ ϝιου NFUIPE ͸ ϨγʔόҾ਺Λ࣋ͭؔ਺ GVODUJPO

METHODS ϨγʔόʢSFDFJWFS Ҿ਺ ܕʹϝιου NFUIPE Λ ఆٛ͢Δ͜ͱ͕Ͱ͖Δ ϝιου NFUIPE ͸
ϨγʔόҾ਺Λ࣋ͭؔ਺ GVODUJPO

METHODS ARE FUNCTIONS ࠓճͷ"CTͷΑ͏ͳϝιουͰ͋Ε͹ɺ ؔ਺Ͱදݱͯ͠΋࢖͍উख͸มΘΒͳ͍

METHODS CONTINUED ߏ଄ମ TUSVDU Ͱ͸ͳ͍ܕͰ΋ ϝιουΛఆٛͰ͖Δ

METHODS CONTINUED ߏ଄ମ TUSVDU Ͱ͸ͳ͍ܕͰ΋ ϝιουΛఆٛͰ͖Δ ϝιου͸ɺ ϝιουͱಉ͡ύοέʔδͰ ܕ͕ఆٛ͞Ε͍ͯΔϨγʔόʔͰͷΈఆٛͰ͖Δ ܕ͕ผͷύοέʔδʢJOUͳͲͷ૊ΈࠐΈܕΛؚΉʣͰ
ఆٛ͞Ε͍ͯΔϨγʔόʔͰ ϝιουΛએݴ͢Δ͜ͱ͸Ͱ͖ͳ͍

METHODS CONTINUED ܕ͕ผͷύοέʔδʢJOUͳͲͷ૊ΈࠐΈܕΛؚΉʣͰఆٛ͞Ε͍ͯΔ ϨγʔόʔͰϝιουΛఆٛ͢Δͱʜ

METHODS CONTINUED ৽͘͠UZQFએݴ͢Δ

POINTER RECEIVERS ϙΠϯλʔͷϨγʔόΛ࣋ͭ ϝιου΋ఆٛͰ͖Δ

POINTER AND FUNCTIONS ϝιουΛఆٛͨ͠৔߹ ؔ਺Ͱఆٛͨ͠৔߹ ΞυϨεԋࢉࢠ Λ࢖͏

METHODS AND POINTER INDIRECTION (1) ؒ઀ࢀর

METHODS AND POINTER INDIRECTION (2)

ग़ྗ݁Ռ ऄ଍ ஋ϨγʔόͱϙΠϯλϨγʔόͷҧ͍ ஋ ΞυϨε

CHOOSING A VALUE OR POINTER RECEIVER ϙΠϯλϨγʔόͷϝϦοτ ᶃ ϝιου͕Ϩγʔό͕ࢦ͢஋Λ มߋ͢Δ͜ͱ͕Ͱ͖Δ͜ͱ
ᶄ ؔ਺ΛݺͿ͝ͱʹ ஋ͷίϐʔ͕ൃੜ͢ΔͷΛ ආ͚Δ͜ͱ͕Ͱ͖Δ͜ͱ

休憩タイム

ϝιουͱΠϯλϑΣʔε   

INTERFACES JOUFSGBDF\ "CT GMPBU ^ ϝιουηοτ "CTϝιου΁ͷΠϯλϑΣʔε

INTERFACES JOUFSGBDFܕͷྫ ಉ͡ϝιουηοτ͸ࢦఆͰ͖ͳ͍ ϒϥϯΫࣝผࢠ @ ͸࢖͑ͳ͍ ༷ʑͳϝιουηοτΛࢦఆͰ͖Δ Կ΋ࢦఆ͠ͳ͍ͷ΋ۭͷJOUFSGBDF΋Մೳ Ҿ༻ɿhttps://golang.org/ref/spec#Interface_types

INTERFACES ARE IMPLEMENTED IMPLICITLY ͜ͷϝιου͸5ܕ͸ JOUFSGBDF*Λ࣮૷͍ͯ͠Δ͜ͱ Λҙຯ͍ͯ͠Δ ͔͠͠ɺ࣮૷͍ͯ͠Δ͜ͱΛ ໌ࣔతʹએݴ͢Δඞཁ͕ͳ͍

INTERFACES ARE IMPLEMENTED IMPLICITLY ͜ͷϝιου͸5ܕ͸ JOUFSGBDF*Λ࣮૷͍ͯ͠Δ͜ͱ Λҙຯ͍ͯ͠Δ ͔͠͠ɺ࣮૷͍ͯ͠Δ͜ͱΛ ໌ࣔతʹએݴ͢Δඞཁ͕ͳ͍ OBNFTQBDF4BNQMF\
JOUFSGBDF*\ WPJE. ^ DMBTT5*\ QVCMJDWPJE. \ ^ ^ ^ $ $Ͱ͸ 5Ϋϥε͸JOUFSGBDF*Λ ࣮૷͍ͯ͠Δ͜ͱΛ ໌ࣔతʹએݴ͍ͯ͠Δ ଞݴޠͱͷൺֱ

INTERFACE VALUES ग़ ྗ ݁ Ռ ˠ5ܕͷ.ϝιουΛݺͼग़͢ ˠ'ܕͷ.ϝιουΛݺͼग़͢ JOUFSGBDF஋͸ɺ ஋ͱ۩৅ܕͷλϓϧ
ͱߟ͑Δ͜ͱ͕Ͱ͖Δ

INTERFACE VALUES WITH NIL UNDERLYING VALUES ˠOJM ग़ ྗ ݁
Ռ

INTERFACE VALUES WITH NIL UNDERLYING VALUES ˠOJM ˠ5ϙΠϯλܕͷ ɹ.ϝιουΛݺͼग़͢ ग़
ྗ ݁ Ռ

INTERFACE VALUES WITH NIL UNDERLYING VALUES ˠOJM ˠ5ϙΠϯλܕͷ ɹ.ϝιουΛݺͼग़͢ U͸OJMͷͨΊɺ
.ϝιουͷϨγʔό͸ OJMͱͳΔ ग़ ྗ ݁ Ռ

INTERFACE VALUES WITH NIL UNDERLYING VALUES ˠOJM ˠ5ϙΠϯλܕͷ ɹ.ϝιουΛݺͼग़͢ U͸OJMͷͨΊɺ
.ϝιουͷϨγʔό͸ OJMͱͳΔ ग़ ྗ ݁ Ռ OJMϨγʔόͰݺͼग़͞ΕΔ͜ͱ Λద੾ʹॲཧ͍ͯ͠Δ

ग़ ྗ ݁ Ռ NIL INTERFACE VALUES JOUFSGBDFܕͷ ॳظԽ͞Ε͍ͯͳ͍ม਺ͷ஋͸OJMͰ͋Δ ͜ͷม਺͸ɺ·ͩ஋΋۩৅ܕ΋อ࣋͠ͳ͍
͜ͷ··ͰϝιουΛݺͼग़͢ͱɺ Ͳͷ۩ମతͳϝιουΛݺͼग़͔͢Λࣔ͢ܕ৘ใ͕ JOUFSGBDFλϓϧ಺ʹͳ͍ͨΊɺ࣮ߦ࣌ΤϥʔʹͳΔ

THE EMPTY INTERFACE ۭͷJOUFSGBDF

THE EMPTY INTERFACE ۭͷJOUFSGBDF ϝιουηοτΛ࣋ͨͳ͍

THE EMPTY INTERFACE ۭͷJOUFSGBDF ϝιουηοτΛ࣋ͨͳ͍ ೚ҙͷλΠϓͷ஋Λอ࣋Ͱ͖Δ

TYPE ASSERTIONS ܕΞαʔγϣϯ͸ɺ JOUFSGBDF஋ͷجૅͱͳΔ ۩ମతͳ஋΁ͷΞΫηεΛఏڙ͢Δ

TYPE ASSERTIONS ܕΞαʔγϣϯ͸ɺ JOUFSGBDF஋ͷجૅͱͳΔ ۩ମతͳ஋΁ͷΞΫηεΛఏڙ͢Δ JOUFSGBDF஋J͕۩৅ܕ5Λอ࣋͠ɺ جʹͳΔ5஋Λม਺UʹׂΓ౰ͯΔ͜ͱΛ ද໌͍ͯ͠Δ ग़ྗ݁Ռ

TYPE ASSERTIONS ܕΞαʔγϣϯ͸ɺ JOUFSGBDF஋ͷجૅͱͳΔ ۩ମతͳ஋΁ͷΞΫηεΛఏڙ͢Δ ग़ྗ݁Ռ J͕5Λอ͍࣋ͯ͠ͳ͍৔߹͸ɺ QBOJD͕ൃੜ͢Δ

TYPE ASSERTIONS ܕΞαʔγϣϯ͸ɺ JOUFSGBDF஋ͷجૅͱͳΔ ۩ମతͳ஋΁ͷΞΫηεΛఏڙ͢Δ JOUFSGBDF஋͕ಛఆͷܕΛอ͍࣋ͯ͠Δ͔Ͳ͏͔Λςετ͢ΔͨΊʹɺ ܕΞαʔγϣϯ͸ҎԼͷͭͷ஋Λฦ͢ ɾجͱͳΔ஋ ɾΞαʔγϣϯ͕੒ޭ͔ͨ͠Ͳ͏͔Λใࠂ͢ΔCPPM஋

TYPE ASSERTIONS ܕΞαʔγϣϯ͸ɺ JOUFSGBDF஋ͷجૅͱͳΔ ۩ମతͳ஋΁ͷΞΫηεΛఏڙ͢Δ JOUFSGBDF஋͕ಛఆͷܕΛอ͍࣋ͯ͠Δ͔Ͳ͏͔Λςετ͢ΔͨΊʹɺ ܕΞαʔγϣϯ͸ҎԼͷͭͷ஋Λฦ͢ ɾجͱͳΔ஋ ɾΞαʔγϣϯ͕੒ޭ͔ͨ͠Ͳ͏͔Λใࠂ͢ΔCPPM஋ ग़ྗ݁Ռ
J͕5Λอ͍࣋ͯ͠Δ৔߹ɺ U͸جʹͳΔ஋ͱͳΓɺPL͸USVFʹͳΔ

TYPE ASSERTIONS ܕΞαʔγϣϯ͸ɺ JOUFSGBDF஋ͷجૅͱͳΔ ۩ମతͳ஋΁ͷΞΫηεΛఏڙ͢Δ JOUFSGBDF஋͕ಛఆͷܕΛอ͍࣋ͯ͠Δ͔Ͳ͏͔Λςετ͢ΔͨΊʹɺ ܕΞαʔγϣϯ͸ҎԼͷͭͷ஋Λฦ͢ ɾجͱͳΔ஋ ɾΞαʔγϣϯ͕੒ޭ͔ͨ͠Ͳ͏͔Λใࠂ͢ΔCPPM஋ ग़ྗ݁Ռ
J͕5Λอ͍࣋ͯ͠ͳ͍৔߹ɺ U͸5ܕͷθϩ஋ͱͳΓɺPL͸GBMTFʹͳΔ QBOJD͸ى͖ͳ͍

TYPE SWITCHES ۭͷJOUFSGBDF͸ܕ৘ใ͕গͳ͍

TYPE SWITCHES ۭͷJOUFSGBDF͸ܕ৘ใ͕গͳ͍ ܕΞαʔγϣϯͱTXJUDIจΛ࢖ͬͯ ܕ͝ͱͷॲཧΛߦ͑Δ

ϝιουͱΠϯλϑΣʔε  ΠϯλϑΣʔεͷྫ 

STRINGERS ࠷΋ҰൠతͳJOUFSGBDFͷͭ͸ɺ GNUύοέʔδͰఆٛ͞Εͨ4USJOHFS 4USJOHFS͸ɺ ͦΕࣗମΛจࣈྻͱͯ͠ هड़͢Δ͜ͱ͕Ͱ͖ΔܕͰ͋Δ GNUύοέʔδʢ͓Αͼଞͷଟ͘ʣ͸ɺ ஋Λग़ྗ͢ΔͨΊʹ͜ͷJOUFSGBDFΛ୳͢

ERRORS (PͷϓϩάϥϜͰ͸ Τϥʔঢ়ଶΛFSSPS஋Ͱද͢ FSSPSܕ͸ ૊ࠐ CVJMUJO JOUFSGBDFͰ GNU4USJOHFSʹܗ͕ࣅ͍ͯΔ ༨ஊɿ GNU4USJOHFSಉ༷ʹɺ
GNUύοέʔδ͸ɺ ஋Λग़ྗ͢Δ࣌FSSPSJOUFSGBDFΛ୳͢

ERRORS (PͷϓϩάϥϜͰ͸ Τϥʔঢ়ଶΛFSSPS஋Ͱද͢ FSSPSܕ͸ ૊ࠐ CVJMUJO JOUFSGBDFͰ GNU4USJOHFSʹܗ͕ࣅ͍ͯΔ ༨ஊɿ GNU4USJOHFSಉ༷ʹɺ
GNUύοέʔδ͸ɺ ஋Λग़ྗ͢Δ࣌FSSPSJOUFSGBDFΛ୳͢ ؔ਺͸ଟ͘ͷ৔߹Τϥʔ஋Λฦ͠ɺ ݺͼग़͠ίʔυ͸ Τϥʔ͕OJMʹ౳͍͔͠Ͳ͏͔Λςετ͢Δ͜ͱͰ ΤϥʔΛॲཧ͢Δඞཁ͕͋Δ OJMFSSPS͸੒ޭΛࣔ͠ɺඇOJMFSSPS͸ࣦഊΛࣔ͢

READERS JPύοέʔδ͸ɺ σʔλͷετϦʔϜͷಡΈऔΓऴྃΛද͢ JP3FBEFSJOUFSGBDFΛنఆ͍ͯ͠Δ (Pඪ४ϥΠϒϥϦʹ͸ɺ ϑΝΠϧɺωοτϫʔΫ઀ଓɺ ίϯϓϨοαʔɺ҉߸ͳͲ ΛؚΉ͜ΕΒͷJOUFSGBDFͷ ଟ͘ͷ࣮૷ؚ͕·Ε͍ͯΔ JP3FBEFSJOUFSGBDFʹ͸
3FBEϝιου͕͋Δ 3FBE͸ɺ ࢦఆ͞ΕͨόΠτεϥΠεʹσʔλΛಡΈࠐΈɺ ಡΈࠐ·ΕͨόΠτ਺ͱΤϥʔ஋Λฦ͢͠ ετϦʔϜ͕ऴྃ͢ΔͱɺJP&0'ΤϥʔΛฦ͢ ग़ྗ݁Ռ

IMAGES JNBHFύοέʔδ͸ɺ *NBHFJOUFSGBDFΛఆٛ͢Δ ஫ɿ#PVOETϝιουͷ3FDUBOHMF໭Γ஋͸ɺ એݴ͕JNBHFύοέʔδ಺ʹ͋ΔͨΊɺ ࣮ࡍʹ͸JNBHF3FDUBOHMFͰ͋Δ

IMAGES JNBHFύοέʔδ͸ɺ *NBHFJOUFSGBDFΛఆٛ͢Δ ஫ɿ#PVOETϝιουͷ3FDUBOHMF໭Γ஋͸ɺ એݴ͕JNBHFύοέʔδ಺ʹ͋ΔͨΊɺ ࣮ࡍʹ͸JNBHF3FDUBOHMFͰ͋Δ Ҿ༻ɿhttps://golang.org/src/image/color/color.go

IMAGES JNBHFύοέʔδ͸ɺ *NBHFJOUFSGBDFΛఆٛ͢Δ Ҿ༻ɿhttps://golang.org/src/image/image.go ஫ɿ#PVOETϝιουͷ3FDUBOHMF໭Γ஋͸ɺ એݴ͕JNBHFύοέʔδ಺ʹ͋ΔͨΊɺ ࣮ࡍʹ͸JNBHF3FDUBOHMFͰ͋Δ Ҿ༻ɿhttps://golang.org/src/image/color/color.go

IMAGES JNBHFύοέʔδ͸ɺ *NBHFJOUFSGBDFΛఆٛ͢Δ Ҿ༻ɿhttps://golang.org/src/image/image.go ஫ɿ#PVOETϝιουͷ3FDUBOHMF໭Γ஋͸ɺ એݴ͕JNBHFύοέʔδ಺ʹ͋ΔͨΊɺ ࣮ࡍʹ͸JNBHF3FDUBOHMFͰ͋Δ Ҿ༻ɿhttps://golang.org/src/image/color/color.go Ҿ༻ɿhttps://golang.org/src/image/image.go

IMAGES JNBHFύοέʔδ͸ɺ *NBHFJOUFSGBDFΛఆٛ͢Δ Ҿ༻ɿhttps://golang.org/src/image/image.go ஫ɿ#PVOETϝιουͷ3FDUBOHMF໭Γ஋͸ɺ એݴ͕JNBHFύοέʔδ಺ʹ͋ΔͨΊɺ ࣮ࡍʹ͸JNBHF3FDUBOHMFͰ͋Δ Ҿ༻ɿhttps://golang.org/src/image/color/color.go Ҿ༻ɿhttps://golang.org/src/image/image.go Ҿ༻ɿhttps://golang.org/src/image/color/color.go

ҰॹʹಡΉͱྑ͍هࣄ w GVODܦ༝ͰJOUFSGBDFܕʹOJMΛೖΕΔͱɺOJMѻ͍ʹͳΒͳ͍ɻ IUUQTRJJUBDPNSFJLJJUFNTGFBDFBEE w (PMBOHͷOJMʹ͍ͭͯ IUUQTDISJTUJOBIBUFOBCMPHDPNFOUSZ
w CVJMEXFCBQQMJDBUJPOXJUIHPMBOH IUUQTHJUIVCDPNBTUBYJFCVJMEXFCBQQMJDBUJPOXJUIHPMBOHCMPCNBTUFSKBQSFGBDFNE w (PݴޠۭΠϯλʔϑΣʔεͱܕΞαʔγϣϯ IUUQTCMPHZZVLJOFUFOUSZ w (PMBOH଎शJOUFSGBDF\^ܕͱJOUFSGBDF IUUQTRJJUBDPNTIUBUTVOPJUFNTDDFBFBGEGEG

THANKS • "5PVSPG(P IUUQUPVSHPMBOHPSH • "5PVSPG(P ೔ຊޠ຋༁൛ IUUQTHPUPVSKQBQQTQPUDPN
• HPQIFSJ[FNF IUUQTHPQIFSJ[FNF • FHPOFMCSFHPQIFST IUUQTHJUIVCDPNFHPOFMCSFHPQIFST • BTIMFZNDOBNBSBHPQIFST IUUQTHJUIVCDPNBTIMFZNDOBNBSBHPQIFST

EngineerX.go#2 - A Tour of Goで一緒にGo入門 : メソッドとイン...

EngineerX.go#2 - A Tour of Goで一緒にGo入門 : メソッドとインタフェース編 -

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