update book code

eBook/examples/chapter_11/cars.go

@@ -0,0 +1,95 @@
+// cars.go
+package main
+
+import (
+	"fmt"
+)
+
+
+type Any interface{}
+type Car struct {
+	Model   	string
+	Manufacturer	string
+	BuildYear	int
+    // ...
+}
+type Cars []*Car
+
+func main() {
+	// make some cars:
+	ford := &Car{"Fiesta","Ford", 2008}
+	bmw  := &Car{"XL 450", "BMW", 2011}
+	merc := &Car{"D600", "Mercedes", 2009}
+	bmw2 := &Car{"X 800", "BMW", 2008}
+	// query:
+	allCars := Cars([]*Car{ford, bmw, merc, bmw2})
+	allNewBMWs := allCars.FindAll(func(car *Car) bool {
+      return (car.Manufacturer == "BMW") && (car.BuildYear > 2010)
+	})
+	fmt.Println("AllCars: ", allCars)
+	fmt.Println("New BMWs: ", allNewBMWs)
+	//
+	manufacturers := []string{"Ford", "Aston Martin", "Land Rover", "BMW", "Jaguar"}
+	sortedAppender, sortedCars := MakeSortedAppender(manufacturers)
+	allCars.Process(sortedAppender)
+	fmt.Println("Map sortedCars: ", sortedCars)
+    BMWCount := len(sortedCars["BMW"])
+	fmt.Println("We have ", BMWCount, " BMWs")
+}
+
+// Process all cars with the given function f:
+func (cs Cars) Process(f func(car *Car)) {
+     for _, c := range cs {
+         f(c)
+     }
+}
+
+// Find all cars matching a given criteria.
+func (cs Cars) FindAll(f func(car *Car) bool) Cars {
+    cars := make([]*Car, 0)
+
+    cs.Process(func(c *Car) {
+        if f(c) {
+            cars = append(cars, c)
+        }
+    })
+    return cars
+}
+
+// Process cars and create new data.
+func (cs Cars) Map(f func(car *Car) Any) []Any {
+       result := make([]Any, 0)
+       ix := 0
+       cs.Process(func(c *Car) {
+           result[ix] = f(c)
+           ix++
+       })
+       return result
+}
+
+func MakeSortedAppender(manufacturers []string) (func(car *Car), map[string]Cars) {
+     // Prepare maps of sorted cars.
+       sortedCars := make(map[string]Cars)
+   
+       for _, m := range manufacturers {
+           sortedCars[m] = make([]*Car, 0)
+       }
+       sortedCars["Default"] = make([]*Car, 0)
+   
+       // Prepare appender function:
+       appender := func(c *Car) {
+           if _, ok := sortedCars[c.Manufacturer]; ok {
+               sortedCars[c.Manufacturer] = append(sortedCars[c.Manufacturer], c)
+           } else {
+               sortedCars["Default"] = append(sortedCars["Default"], c)
+           }
+       }
+       return appender, sortedCars
+}
+
+/* Output:
+AllCars:  [0xf8400038a0 0xf840003bd0 0xf840003ba0 0xf840003b70]
+New BMWs:  [0xf840003bd0]
+Map sortedCars:  map[Default:[0xf840003ba0] Jaguar:[] Land Rover:[] BMW:[0xf840003bd0 0xf840003b70] Aston Martin:[] Ford:[0xf8400038a0]]
+We have  2  BMWs
+*/