エラーハンドリング
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<span class="k">package</span> <span class="n">main</span> <span class="k">import</span> <span class="p">(</span> <span class="s">"fmt"</span> <span class="s">"log"</span> <span class="s">"os"</span> <span class="p">)</span> <span class="k">func</span> <span class="n">main</span><span class="p">()</span> <span class="p">{</span> <span class="n">file</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">os</span><span class="o">.</span><span class="n">Open</span><span class="p">(</span><span class="s">"./tt.go"</span><span class="p">)</span> <span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span> <span class="n">log</span><span class="o">.</span><span class="n">Fatalln</span><span class="p">(</span><span class="s">"Error"</span><span class="p">)</span> <span class="p">}</span> <span class="k">defer</span> <span class="n">file</span><span class="o">.</span><span class="n">Close</span><span class="p">()</span> <span class="n">data</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="m">100</span><span class="p">)</span> <span class="c">// errは上書きでinicializeしている</span> <span class="n">count</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">file</span><span class="o">.</span><span class="n">Read</span><span class="p">(</span><span class="n">data</span><span class="p">)</span> <span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span> <span class="n">log</span><span class="o">.</span><span class="n">Fatalln</span><span class="p">(</span><span class="s">"Error"</span><span class="p">)</span> <span class="p">}</span> <span class="n">fmt</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">count</span><span class="p">,</span> <span class="kt">string</span><span class="p">(</span><span class="n">data</span><span class="p">))</span> <span class="p">}</span> |
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2020/06/19 08:37:42 Error |
パニック
- 例外エラーの中の例外
- 何をしたらいいかわからない状態なのでなるべくエラーハンドリングするとよい
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<span class="k">package</span> <span class="n">main</span> <span class="k">import</span> <span class="s">"fmt"</span> <span class="c">// DB接続パッケージ</span> <span class="k">func</span> <span class="n">thirdPirtyConnectDB</span><span class="p">()</span> <span class="p">{</span> <span class="nb">panic</span><span class="p">(</span><span class="s">"Unable to connect database"</span><span class="p">)</span> <span class="p">}</span> <span class="k">func</span> <span class="n">save</span><span class="p">()</span> <span class="p">{</span> <span class="c">// 強制終了させないようにrecoverする</span> <span class="k">defer</span> <span class="k">func</span><span class="p">()</span> <span class="p">{</span> <span class="n">s</span> <span class="o">:=</span> <span class="nb">recover</span><span class="p">()</span> <span class="n">fmt</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">s</span><span class="p">)</span> <span class="p">}()</span> <span class="n">thirdPirtyConnectDB</span><span class="p">()</span> <span class="p">}</span> <span class="k">func</span> <span class="n">main</span><span class="p">()</span> <span class="p">{</span> <span class="n">save</span><span class="p">()</span> <span class="n">fmt</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="s">"OK?"</span><span class="p">)</span> <span class="p">}</span> |
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Unable to connect database OK? |