Error handling examples

.gitignore

@@ -42,3 +42,5 @@ Cargo.lock
 **/*.rs.bk
 
 # End of https://www.gitignore.io/api/osx,rust
+
+errors/hello.txt

.idea/misc.xml

@@ -15,6 +15,7 @@
     <cargoProject FILE="$PROJECT_DIR$/rectangles/Cargo.toml" />
     <cargoProject FILE="$PROJECT_DIR$/enums/Cargo.toml" />
     <cargoProject FILE="$PROJECT_DIR$/modules/Cargo.toml" />
+    <cargoProject FILE="$PROJECT_DIR$/errors/Cargo.toml" />
   </component>
   <component name="ComposerJsonPluginSettings">
     <unboundedVersionInspectionSettings>

.idea/rust.iml

@@ -59,9 +59,14 @@
       <sourceFolder url="file://$MODULE_DIR$/modules/examples" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/modules/tests" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/modules/benches" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/errors/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/errors/examples" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/errors/tests" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/errors/benches" isTestSource="true" />
       <excludeFolder url="file://$MODULE_DIR$/branches/target" />
       <excludeFolder url="file://$MODULE_DIR$/ctof/target" />
       <excludeFolder url="file://$MODULE_DIR$/enums/target" />
+      <excludeFolder url="file://$MODULE_DIR$/errors/target" />
       <excludeFolder url="file://$MODULE_DIR$/ftoc/target" />
       <excludeFolder url="file://$MODULE_DIR$/functions/target" />
       <excludeFolder url="file://$MODULE_DIR$/guessing_game/target" />

.idea/workspace.xml

@@ -3,6 +3,9 @@
   <component name="ChangeListManager">
     <list default="true" id="c8f42924-1cd2-4b1c-bcff-602a3368bb16" name="Default Changelist" comment="">
       <change beforePath="$PROJECT_DIR$/.gitignore" beforeDir="false" afterPath="$PROJECT_DIR$/.gitignore" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/misc.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/misc.xml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/rust.iml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/rust.iml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
     </list>
     <option name="EXCLUDED_CONVERTED_TO_IGNORED" value="true" />
     <option name="SHOW_DIALOG" value="false" />
@@ -13,10 +16,14 @@
   <component name="FileEditorManager">
     <leaf SIDE_TABS_SIZE_LIMIT_KEY="300">
       <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/guessing_game/.gitignore">
+        <entry file="file://$PROJECT_DIR$/errors/src/main.rs">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="32">
+            <state relative-caret-position="1024">
-              <caret line="2" column="5" selection-start-line="2" selection-start-column="5" selection-end-line="2" selection-end-column="5" />
+              <caret line="64" column="1" lean-forward="true" selection-start-line="64" selection-start-column="1" selection-end-line="64" selection-end-column="1" />
+              <folding>
+                <element signature="e#285#286#0" expanded="true" />
+                <element signature="e#323#324#0" expanded="true" />
+              </folding>
             </state>
           </provider>
         </entry>
@@ -24,8 +31,8 @@
       <file pinned="false" current-in-tab="true">
         <entry file="file://$PROJECT_DIR$/.gitignore">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="544">
+            <state relative-caret-position="720">
-              <caret line="34" column="12" selection-start-line="34" selection-start-column="12" selection-end-line="34" selection-end-column="12" />
+              <caret line="45" column="16" selection-start-line="45" selection-start-column="16" selection-end-line="45" selection-end-column="16" />
             </state>
           </provider>
         </entry>
@@ -70,6 +77,7 @@
         <option value="$PROJECT_DIR$/modules/src/main.rs" />
         <option value="$PROJECT_DIR$/modules/src/sound/instrument.rs" />
         <option value="$PROJECT_DIR$/guessing_game/.gitignore" />
+        <option value="$PROJECT_DIR$/errors/src/main.rs" />
         <option value="$PROJECT_DIR$/.gitignore" />
       </list>
     </option>
@@ -101,6 +109,11 @@
               <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
               <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
             </path>
+            <path>
+              <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
+              <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
+              <item name="errors" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+            </path>
           </expand>
           <select />
         </subPane>
@@ -132,7 +145,7 @@
   </component>
   <component name="PropertiesComponent">
     <property name="JavaScriptWeakerCompletionTypeGuess" value="true" />
-    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1548879647202" />
+    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1548883606455" />
     <property name="javascript.nodejs.core.library.configured.version" value="7.1.0" />
     <property name="js.eslint.eslintPackage" value="$USER_HOME$/.yarn-config/global/node_modules/.bin/eslint" />
     <property name="js.eslint.nodeInterpreter" value="project" />
@@ -160,7 +173,7 @@
       </list>
     </option>
   </component>
-  <component name="RunManager" selected="Cargo Command.Run modules">
+  <component name="RunManager" selected="Cargo Command.Run errors">
     <configuration name="&lt;template&gt;" type="TestNG" default="true" selected="false">
       <option name="MAIN_CLASS_NAME" />
       <option name="VM_PARAMETERS" value="-ea" />
@@ -189,6 +202,16 @@
       <envs />
       <method v="2" />
     </configuration>
+    <configuration name="Run errors" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
+      <option name="channel" value="DEFAULT" />
+      <option name="command" value="run --package errors --bin errors" />
+      <option name="allFeatures" value="false" />
+      <option name="nocapture" value="false" />
+      <option name="backtrace" value="SHORT" />
+      <option name="workingDirectory" value="file://$PROJECT_DIR$/errors" />
+      <envs />
+      <method v="2" />
+    </configuration>
     <configuration name="Run modules" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
       <option name="channel" value="DEFAULT" />
       <option name="command" value="run --package modules --bin modules" />
@@ -209,16 +232,6 @@
       <envs />
       <method v="2" />
     </configuration>
-    <configuration name="Run slices" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
-      <option name="channel" value="DEFAULT" />
-      <option name="command" value="run --package slices --bin slices" />
-      <option name="allFeatures" value="false" />
-      <option name="nocapture" value="false" />
-      <option name="backtrace" value="SHORT" />
-      <option name="workingDirectory" value="file://$PROJECT_DIR$/slices" />
-      <envs />
-      <method v="2" />
-    </configuration>
     <configuration name="Run structs" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
       <option name="channel" value="DEFAULT" />
       <option name="command" value="run --package structs --bin structs" />
@@ -238,11 +251,11 @@
     </configuration>
     <recent_temporary>
       <list>
+        <item itemvalue="Cargo Command.Run errors" />
         <item itemvalue="Cargo Command.Run modules" />
         <item itemvalue="Cargo Command.Run enums" />
         <item itemvalue="Cargo Command.Run rectangles" />
         <item itemvalue="Cargo Command.Run structs" />
-        <item itemvalue="Cargo Command.Run slices" />
       </list>
     </recent_temporary>
   </component>
@@ -258,7 +271,7 @@
       <window_info id="Favorites" order="5" side_tool="true" />
       <window_info id="Cargo" order="6" sideWeight="0.49791494" weight="0.3286119" />
       <window_info anchor="bottom" id="Message" order="0" />
-      <window_info anchor="bottom" id="Find" order="1" />
+      <window_info anchor="bottom" id="Find" order="1" weight="0.32979318" />
       <window_info anchor="bottom" id="Run" order="2" visible="true" weight="0.32979318" />
       <window_info anchor="bottom" id="Debug" order="3" weight="0.4" />
       <window_info anchor="bottom" id="Cvs" order="4" weight="0.25" />
@@ -438,10 +451,24 @@
         </state>
       </provider>
     </entry>
+    <entry file="file://$PROJECT_DIR$/errors/hello.txt">
+      <provider selected="true" editor-type-id="text-editor" />
+    </entry>
+    <entry file="file://$PROJECT_DIR$/errors/src/main.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="1024">
+          <caret line="64" column="1" lean-forward="true" selection-start-line="64" selection-start-column="1" selection-end-line="64" selection-end-column="1" />
+          <folding>
+            <element signature="e#285#286#0" expanded="true" />
+            <element signature="e#323#324#0" expanded="true" />
+          </folding>
+        </state>
+      </provider>
+    </entry>
     <entry file="file://$PROJECT_DIR$/.gitignore">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="544">
+        <state relative-caret-position="720">
-          <caret line="34" column="12" selection-start-line="34" selection-start-column="12" selection-end-line="34" selection-end-column="12" />
+          <caret line="45" column="16" selection-start-line="45" selection-start-column="16" selection-end-line="45" selection-end-column="16" />
         </state>
       </provider>
     </entry>

errors/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "errors"
+version = "0.1.0"
+authors = ["Timothy Warren <twarren@nabancard.com>"]
+edition = "2018"
+
+[dependencies]

errors/src/main.rs

@@ -0,0 +1,65 @@
+use std::fs;
+use std::fs::File;
+use std::io::{Error, ErrorKind, Read};
+
+fn main() {
+    let _str = handle_errors_with_match();
+
+    let _str = match handle_errors_with_closures() {
+        Ok(_) => println!("Opened or created the file successfully!"),
+        Err(e) => panic!("There was a problem opening the file: {:?}", e),
+    };
+
+    let _str = match read_username_from_file() {
+        Ok(_) => println!("Opened or created the file successfully!"),
+        Err(e) => panic!("There was a problem opening the file: {:?}", e),
+    };
+
+    let _str = match easy_mode() {
+        Ok(_) => println!("Opened or created the file successfully!"),
+        Err(e) => panic!("There was a problem opening the file: {:?}", e),
+    };
+}
+
+fn easy_mode() -> Result<String, Error> {
+    fs::read_to_string("hello.txt")
+}
+
+fn read_username_from_file() -> Result<String, Error> {
+    let mut s = String::new();
+
+    File::open("hello.txt")?.read_to_string(&mut s)?;
+
+    Ok(s)
+}
+
+fn handle_errors_with_closures () -> Result<File, File> {
+    File::open("hello.txt").map_err(|error| {
+        if error.kind() == ErrorKind::NotFound {
+            File::create("hello.txt").unwrap_or_else(|error| {
+                panic!("Tried to create file but there was a problem: {:?}", error);
+            })
+        } else {
+            panic!("There was a problem opening the file: {:?}", error);
+        }
+    })
+}
+
+fn handle_errors_with_match () -> File {
+    let f = File::open("hello.txt");
+
+    let f = match f {
+        Ok(file) => file,
+        Err(error) => match error.kind() {
+            ErrorKind::NotFound => match File::create("hello.txt") {
+                Ok(fc) => fc,
+                Err(e) => panic!("Tried to create file but there was a problem: {:?}", e),
+            },
+            other_error => panic!("There was a problem opening the file: {:?}", other_error),
+        },
+    };
+
+    println!("Opened or created the file successfully!");
+
+    f
+}