update 11.14 (#504)

This commit is contained in:
xin zhao
2018-06-10 11:17:36 +08:00
committed by 无闻
parent 8647473d4f
commit 8451d2cf3f

View File

@@ -1,4 +1,4 @@
# 结构体、集合和高阶函数
# 11.14 结构体、集合和高阶函数
通常你在应用中定义了一个结构体,那么你也可能需要这个结构体的(指针)对象集合,比如:
@@ -48,13 +48,13 @@ func (cs Cars) FindAll(f func(car *Car) bool) Cars {
```go
// 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
result := make([]Any, 0)
ix := 0
cs.Process(func(c *Car) {
result[ix] = f(c)
ix++
})
return result
}
```
@@ -62,7 +62,7 @@ func (cs Cars) Map(f func(car *Car) Any) []Any {
```go
allNewBMWs := allCars.FindAll(func(car *Car) bool {
return (car.Manufacturer == "BMW") && (car.BuildYear > 2010)
return (car.Manufacturer == "BMW") && (car.BuildYear > 2010)
})
```
@@ -84,7 +84,7 @@ func MakeSortedAppender(manufacturers[]string)(func(car*Car),map[string]Cars) {
sortedCars["Default"] = append(sortedCars["Default"], c)
}
}
}
return appender, sortedCars
}
```
@@ -112,23 +112,23 @@ import (
type Any interface{}
type Car struct {
Model string
Manufacturer string
BuildYear int
// ...
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}
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)
return (car.Manufacturer == "BMW") && (car.BuildYear > 2010)
})
fmt.Println("AllCars: ", allCars)
fmt.Println("New BMWs: ", allNewBMWs)
@@ -137,58 +137,58 @@ func main() {
sortedAppender, sortedCars := MakeSortedAppender(manufacturers)
allCars.Process(sortedAppender)
fmt.Println("Map sortedCars: ", sortedCars)
BMWCount := len(sortedCars["BMW"])
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)
}
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)
cars := make([]*Car, 0)
cs.Process(func(c *Car) {
if f(c) {
cars = append(cars, c)
}
})
return cars
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, len(cs))
ix := 0
cs.Process(func(c *Car) {
result[ix] = f(c)
ix++
})
return result
result := make([]Any, len(cs))
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)
// Prepare maps of sorted cars.
sortedCars := make(map[string]Cars)
for _, m := range manufacturers {
sortedCars[m] = make([]*Car, 0)
}
sortedCars["Default"] = make([]*Car, 0)
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
// 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
}
```