{"id":823,"date":"2020-03-22T13:48:30","date_gmt":"2020-03-22T04:48:30","guid":{"rendered":"https:\/\/www.itchefblog.com\/?p=823"},"modified":"2020-12-31T23:50:52","modified_gmt":"2020-12-31T14:50:52","slug":"kotlin-%eb%b3%80%ec%88%98%ec%97%90-null-%ed%95%a0%eb%8b%b9%ed%95%98%ea%b8%b0","status":"publish","type":"post","link":"https:\/\/www.itchefblog.com\/?p=823","title":{"rendered":"kotlin \ubcc0\uc218\uc5d0 null \ud560\ub2f9\ud558\uae30"},"content":{"rendered":"\n

kotlin\uc740 \uae30\ubcf8\uc801\uc73c\ub85c NPE free\ud558\uac8c \uc124\uacc4\uac00 \ub418\uc5b4\uc11c \ubcc0\uc218\uc5d0 null\uc744 \ud560\ub2f9\ud560 \uc218 \uc5c6\ub2e4.<\/p>\n\n\n\n

val name: String = null<\/pre>

\uc704\uc640 \uac19\uc774 \uc120\uc5b8\ud558\uba74 \uc624\ub958\uac00 \ubc1c\uc0dd\ud55c\ub2e4.

\ud558\uc9c0\ub9cc null\uc744 \ud5c8\uc6a9\ud574\uc57c \ud558\ub294 \uacbd\uc6b0\ub77c\uba74?
\ub2e4\uc74c\uacfc \uac19\uc774 \uc790\ub8cc\ud615\uc5d0 ?\ub97c \ubd99\uc5ec\uc8fc\uba74 \ud574\ub2f9 \ubcc0\uc218\uc5d0 null\uc744 \ud560\ub2f9\ud560 \uc218 \uc788\ub2e4.<\/p>\n\n\n\n
val name: String? = null<\/pre><\/p>\n\n\n\n
?\ub85c \uc120\uc5b8\ud55c \ubcc0\uc218\uc5d0 null \uac12\uc774 \ub4e4\uc5b4\uc788\ub294 \uc0c1\ud0dc\uc5d0\uc11c \ud574\ub2f9 \ubcc0\uc218\ub97c \ud638\ucd9c\ud558\uba74?
\ub2f9\uc5f0\ud558\uac8c\ub3c4 NPE\uac00 \ubc1c\uc0dd\ud55c\ub2e4. \uc774\ub97c \ubc29\uc9c0\ud558\uae30 \uc704\ud574\uc11c safe call\uc774 \uc874\uc7ac\ud55c\ub2e4.

name.length \ub97c \ud638\ucd9c\ud558\uba74 NPE\uac00 \ubc1c\uc0dd\ud558\uc9c0\ub9cc name?.length\uc640 \uac19\uc774 \ud638\ucd9c\ud558\uba74
name\uc5d0 \uac12\uc774 \uc788\ub2e4\uba74 length\uc5d0 \uc811\uadfc\ud574\uc11c \uac12\uc744 \uc77d\uc5b4\uc11c \uacb0\uacfc\ub97c \ubc18\ud658\ud558\uace0, \uc544\ubb34 \uac12\uc774 \uc5c6\uc73c\uba74 \uadf8\ub0e5 null\uc744 \ubc18\ud658\ud55c\ub2e4.<\/p>\n\n\n\n
?. (safe call)\uc744 \uc0ac\uc6a9\ud558\uba74 null \uac12\uc744 \ubcf4\ub2e4 \uc548\uc804\ud558\uac8c \uc0ac\uc6a9\ud560 \uc218 \uc788\ub2e4.<\/p>\n\n\n\n
\ub610\ud55c \ub2e8\uc815 \uae30\ud638\uc778 !!\ub3c4 \uc0ac\uc6a9\ud560 \uc218 \uc788\ub294\ub370, \uc774 \uae30\ud638\ub294 \ud504\ub85c\uadf8\ub798\uba38\uac00 \ubcc0\uc218\uc5d0 \ud560\ub2f9\ub41c \uac12\uc774 null\uc774 \uc544\ub2d8\uc744 \ub2e8\uc815\ud558\ub294 \uae30\ud638\ub85c\uc368 \ucf54\ub529 \uc2dc\uc5d0\ub294 \uc624\ub958\uac00 \ubc1c\uc0dd\ud558\uc9c0 \uc54a\uc9c0\ub9cc \uc2e4\ud589 \uc2dc\uc5d0 \uac12\uc774 null\uc774\uba74 NPE\ub97c \ubc1c\uc0dd \uc2dc\ud0a8\ub2e4.<\/p>\n\n\n\n
\ub2e4\ub978 \ubc29\ubc95\uc73c\ub85c\ub294 \uc870\uac74\ubb38\uc744 \uc0ac\uc6a9\ud558\uc5ec \ubcc0\uc218\uac00 null\uc774 \uc544\ub2d0 \uacbd\uc6b0 \uc548\uc804\ud558\uac8c \uc0ac\uc6a9\ud558\ub294 \ubc29\ubc95\uc774 \uc788\ub2e4.

if(name != null) name.length else -1<\/pre>

\uc704\uc758 \uacbd\uc6b0 null\uc774 \uc544\ub2c8\uba74 name.length\ub97c \ubc18\ud658\ud558\uace0 null\uc77c \uacbd\uc6b0 -1\uc744 \ubc18\ud658\ud55c\ub2e4.<\/p>\n\n\n\n
safe call\uacfc elvis \uc5f0\uc0b0\uc790\ub97c \ud65c\uc6a9\ud574 null\uc744 \ud5c8\uc6a9\ud55c \ubcc0\uc218\ub97c \ub354 \uc548\uc804\ud558\uac8c \uc0ac\uc6a9\ud558\ub824\ubcc0 \ub2e4\uc74c\uacfc \uac19\uc774 \uc0ac\uc6a9\ud558\uba74 \ub41c\ub2e4.

name?.length ?: -1<\/pre>

\uc704\uc758 \uacbd\uc6b0 name\uc774 null\uc774 \uc544\ub2c8\uba74 ?:\uc758 \uc88c\uce21\uc744, null\uc774\uba74 \uc6b0\uce21\uc744 \ubc18\ud658\ud55c\ub2e4.<\/p>\n","protected":false},"excerpt":{"rendered":"
kotlin\uc740 \uae30\ubcf8\uc801\uc73c\ub85c NPE free\ud558\uac8c \uc124\uacc4\uac00 \ub418\uc5b4\uc11c \ubcc0\uc218\uc5d0 null\uc744 \ud560\ub2f9\ud560 \uc218 \uc5c6\ub2e4. \uc704\uc640 \uac19\uc774 \uc120\uc5b8\ud558\uba74 \uc624\ub958\uac00 \ubc1c\uc0dd\ud55c\ub2e4. \ud558\uc9c0\ub9cc null\uc744 \ud5c8\uc6a9\ud574\uc57c \ud558\ub294 \uacbd\uc6b0\ub77c\uba74?\ub2e4\uc74c\uacfc \uac19\uc774 \uc790\ub8cc\ud615\uc5d0 ?\ub97c \ubd99\uc5ec\uc8fc\uba74 \ud574\ub2f9 \ubcc0\uc218\uc5d0 null\uc744 \ud560\ub2f9\ud560 \uc218 \uc788\ub2e4. ?\ub85c \uc120\uc5b8\ud55c \ubcc0\uc218\uc5d0 null \uac12\uc774 \ub4e4\uc5b4\uc788\ub294 \uc0c1\ud0dc\uc5d0\uc11c \ud574\ub2f9 \ubcc0\uc218\ub97c \ud638\ucd9c\ud558\uba74?\ub2f9\uc5f0\ud558\uac8c\ub3c4 NPE\uac00 \ubc1c\uc0dd\ud55c\ub2e4. \uc774\ub97c \ubc29\uc9c0\ud558\uae30 \uc704\ud574\uc11c safe call\uc774 \uc874\uc7ac\ud55c\ub2e4. name.length \ub97c \ud638\ucd9c\ud558\uba74 NPE\uac00 \ubc1c\uc0dd\ud558\uc9c0\ub9cc name?.length\uc640 … <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[349,7],"tags":[357,397,406,473,474],"_links":{"self":[{"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=\/wp\/v2\/posts\/823"}],"collection":[{"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=823"}],"version-history":[{"count":1,"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=\/wp\/v2\/posts\/823\/revisions"}],"predecessor-version":[{"id":825,"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=\/wp\/v2\/posts\/823\/revisions\/825"}],"wp:attachment":[{"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=823"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=823"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.itchefblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=823"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}