Improving README.md

Because of #988 and #983, I added a do...catch in the usage section, and a production implementation example in the related section.

Author: nathanfallet

README.md

@@ -34,67 +34,79 @@ syntax _and_ intent.
 ```swift
 import SQLite
 
-let db = try Connection("path/to/db.sqlite3")
-
-let users = Table("users")
-let id = Expression<Int64>("id")
-let name = Expression<String?>("name")
-let email = Expression<String>("email")
-
-try db.run(users.create { t in
-    t.column(id, primaryKey: true)
-    t.column(name)
-    t.column(email, unique: true)
-})
-// CREATE TABLE "users" (
-//     "id" INTEGER PRIMARY KEY NOT NULL,
-//     "name" TEXT,
-//     "email" TEXT NOT NULL UNIQUE
-// )
-
-let insert = users.insert(name <- "Alice", email <- "[email protected]")
-let rowid = try db.run(insert)
-// INSERT INTO "users" ("name", "email") VALUES ('Alice', '[email protected]')
-
-for user in try db.prepare(users) {
-    print("id: \(user[id]), name: \(user[name]), email: \(user[email])")
-    // id: 1, name: Optional("Alice"), email: [email protected]
+// Wrap everything in a do...catch to handle errors
+do {
+    let db = try Connection("path/to/db.sqlite3")
+
+    let users = Table("users")
+    let id = Expression<Int64>("id")
+    let name = Expression<String?>("name")
+    let email = Expression<String>("email")
+
+    try db.run(users.create { t in
+        t.column(id, primaryKey: true)
+        t.column(name)
+        t.column(email, unique: true)
+    })
+    // CREATE TABLE "users" (
+    //     "id" INTEGER PRIMARY KEY NOT NULL,
+    //     "name" TEXT,
+    //     "email" TEXT NOT NULL UNIQUE
+    // )
+
+    let insert = users.insert(name <- "Alice", email <- "[email protected]")
+    let rowid = try db.run(insert)
+    // INSERT INTO "users" ("name", "email") VALUES ('Alice', '[email protected]')
+
+    for user in try db.prepare(users) {
+        print("id: \(user[id]), name: \(user[name]), email: \(user[email])")
+        // id: 1, name: Optional("Alice"), email: [email protected]
+    }
+    // SELECT * FROM "users"
+
+    let alice = users.filter(id == rowid)
+
+    try db.run(alice.update(email <- email.replace("mac.com", with: "me.com")))
+    // UPDATE "users" SET "email" = replace("email", 'mac.com', 'me.com')
+    // WHERE ("id" = 1)
+
+    try db.run(alice.delete())
+    // DELETE FROM "users" WHERE ("id" = 1)
+
+    try db.scalar(users.count) // 0
+    // SELECT count(*) FROM "users"
+} catch {
+    print (error)
 }
-// SELECT * FROM "users"
-
-let alice = users.filter(id == rowid)
-
-try db.run(alice.update(email <- email.replace("mac.com", with: "me.com")))
-// UPDATE "users" SET "email" = replace("email", 'mac.com', 'me.com')
-// WHERE ("id" = 1)
-
-try db.run(alice.delete())
-// DELETE FROM "users" WHERE ("id" = 1)
-
-try db.scalar(users.count) // 0
-// SELECT count(*) FROM "users"
 ```
 
 SQLite.swift also works as a lightweight, Swift-friendly wrapper over the C
 API.
 
 ```swift
-let stmt = try db.prepare("INSERT INTO users (email) VALUES (?)")
-for email in ["[email protected]", "[email protected]"] {
-    try stmt.run(email)
+// Wrap everything in a do...catch to handle errors
+do {
+    // ...
+    
+    let stmt = try db.prepare("INSERT INTO users (email) VALUES (?)")
+    for email in ["[email protected]", "[email protected]"] {
+        try stmt.run(email)
+    }
+
+    db.totalChanges    // 3
+    db.changes         // 1
+    db.lastInsertRowid // 3
+
+    for row in try db.prepare("SELECT id, email FROM users") {
+        print("id: \(row[0]), email: \(row[1])")
+        // id: Optional(2), email: Optional("[email protected]")
+        // id: Optional(3), email: Optional("[email protected]")
+    }
+
+    try db.scalar("SELECT count(*) FROM users") // 2
+} catch {
+    print (error)
 }
-
-db.totalChanges    // 3
-db.changes         // 1
-db.lastInsertRowid // 3
-
-for row in try db.prepare("SELECT id, email FROM users") {
-    print("id: \(row[0]), email: \(row[1])")
-    // id: Optional(2), email: Optional("[email protected]")
-    // id: Optional(3), email: Optional("[email protected]")
-}
-
-try db.scalar("SELECT count(*) FROM users") // 2
 ```
 
 [Read the documentation][See Documentation] or explore more,
@@ -253,6 +265,7 @@ These projects enhance or use SQLite.swift:
 
  - [SQLiteMigrationManager.swift][] (inspired by
    [FMDBMigrationManager][])
+ - [Delta: Math helper](https://apps.apple.com/app/delta-math-helper/id1436506800) (see [Delta/Utils/Database.swift](https://github.com/GroupeMINASTE/Delta-iOS/blob/master/Delta/Utils/Database.swift) for production implementation example)
 
 
 ## Alternatives