lancet/docs/function_zh-CN.md

Function

function 函数包控制函数执行流程，包含部分函数式编程。

源码:

https://github.com/duke-git/lancet/blob/v1/function/function.go https://github.com/duke-git/lancet/blob/v1/function/watcher.go

用法:

import (
    "github.com/duke-git/lancet/function"
)

目录

• After
• Before
• Curry
• Compose
• Debounce
• Debounced^deprecated
• Throttle
• Delay
• Pipeline
• Schedule
• Watcher

文档

After

创建一个函数，当他被调用n或更多次之后将马上触发fn

函数签名:

func After(n int, fn interface{}) func(args ...interface{}) []reflect.Value

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    arr := []string{"a", "b"}
    f := function.After(len(arr), func(i int) int {
        fmt.Println("last print")
        return i
    })

    type cb func(args ...interface{}) []reflect.Value
    print := func(i int, s string, fn cb) {
        fmt.Printf("arr[%d] is %s \n", i, s)
        fn(i)
    }

    fmt.Println("arr is", arr)
    for i := 0; i < len(arr); i++ {
        print(i, arr[i], f)
    }

    //output:
    // arr is [a b]
    // arr[0] is a
    // arr[1] is b
    // last print
}

Before

创建一个函数，调用次数不超过n次，之后再调用这个函数，将返回一次最后调用fn的结果

函数签名:

func Before(n int, fn interface{}) func(args ...interface{}) []reflect.Value

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
    "github.com/duke-git/lancet/internal"
)

func main() {
    assert := internal.NewAssert(t, "TestBefore")

    arr := []string{"a", "b", "c", "d", "e"}
    f := function.Before(3, func(i int) int {
        return i
    })

    var res []int64
    type cb func(args ...interface{}) []reflect.Value
    appendStr := func(i int, s string, fn cb) {
        v := fn(i)
        res = append(res, v[0].Int())
    }

    for i := 0; i < len(arr); i++ {
        appendStr(i, arr[i], f)
    }

    expected := []int64{0, 1, 2, 2, 2}
    assert.Equal(expected, res)
}

Curry

创建一个柯里化的函数

函数签名:

type Fn func(...interface{}) interface{}
func (f Fn) Curry(i interface{}) func(...interface{}) interface{}

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    add := func(a, b int) int {
        return a + b
    }
    var addCurry function.Fn = func(values ...interface{}) interface{} {
        return add(values[0].(int), values[1].(int))
    }
    add1 := addCurry.Curry(1)
    result := add1(2)
    fmt.Println(result) //3
}

Compose

从右至左组合函数列表fnList， 返回组合后的函数

函数签名:

func Compose(fnList ...func(...interface{}) interface{}) func(...interface{}) interface{}

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    add1 := func(v ...interface{}) interface{} {
        return v[0].(int) + 1
    }
    add2 := func(v ...interface{}) interface{} {
        return v[0].(int) + 2
    }

    add3 := function.Compose(add1, add2)
    result := add3(1)

    fmt.Println(result) //4
}

Debounce

创建一个函数的去抖动版本。该去抖动函数仅在上次调用后的指定延迟时间过去之后才会调用原始函数。支持取消去抖动。

函数签名:

func Debounce(fn func(), delay time.Duration) (debouncedFn func(), cancelFn func())

示例:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    callCount := 0
    fn := func() {
        callCount++
    }

    debouncedFn, _ := function.Debounce(fn, 500*time.Millisecond)

    for i := 0; i < 10; i++ {
        debouncedFn()
        time.Sleep(50 * time.Millisecond)
    }

    time.Sleep(1 * time.Second)
    fmt.Println(callCount)

    debouncedFn()

    time.Sleep(1 * time.Second)
    fmt.Println(callCount)

    // Output:
    // 1
    // 2
}

Debounced

创建一个 debounced 函数，该函数延迟调用 fn 直到自上次调用 debounced 函数后等待持续时间过去。

函数签名:

func Debounced(fn func(), duration time.Duration) func()

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    count := 0
    add := func() {
        count++
    }

    debouncedAdd := function.Debounced(add, 50*time.Microsecond)
    function.debouncedAdd()
    function.debouncedAdd()
    function.debouncedAdd()
    function.debouncedAdd()

    time.Sleep(100 * time.Millisecond)
    fmt.Println(count) //1

    function.debouncedAdd()
    time.Sleep(100 * time.Millisecond)
    fmt.Println(count) //2
}

Throttle

创建一个函数的节流版本。返回的函数保证在每个时间间隔内最多只会被调用一次。

函数签名:

func Throttle(fn func(), interval time.Duration) func()

示例:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    callCount := 0

    fn := func() {
        callCount++
    }

    throttledFn := function.Throttle(fn, 1*time.Second)

    for i := 0; i < 5; i++ {
        throttledFn()
    }

    time.Sleep(1 * time.Second)

    fmt.Println(callCount)

    // Output:
    // 1
}

Delay

延迟delay时间后调用函数

函数签名:

func Delay(delay time.Duration, fn interface{}, args ...interface{})

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    var print = func(s string) {
        fmt.Println(count) //test delay
    }
    function.Delay(2*time.Second, print, "test delay")
}

Schedule

每次持续时间调用函数，直到关闭返回的 bool chan

函数签名:

func Schedule(d time.Duration, fn interface{}, args ...interface{}) chan bool

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    var res []string
    appendStr := func(s string) {
        res = append(res, s)
    }

    stop := function.Schedule(1*time.Second, appendStr, "*")
    time.Sleep(5 * time.Second)
    close(stop)

    fmt.Println(res) //[* * * * *]
}

Pipeline

管道执行多个函数

函数签名:

func Pipeline(funcs ...func(interface{}) interface{}) func(interface{}) interface{}

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    addOne := func(x interface{}) interface{} {
        return x.(int) + 1
    }
    double := func(x interface{}) interface{} {
        return 2 * x.(int)
    }
    square := func(x interface{}) interface{} {
        return x.(int) * x.(int)
    }

    f := function.Pipeline(addOne, double, square)

    result := fn(2)

    fmt.Println(result)

    // Output:
    // 36
}

Watcher

Watcher 用于记录代码执行时间。可以启动/停止/重置手表定时器。获取函数执行的时间。

函数签名:

type Watcher struct {
    startTime int64
    stopTime  int64
    excuting  bool
}
func (w *Watcher) Start() //start the watcher
func (w *Watcher) Stop() //stop the watcher
func (w *Watcher) Reset() //reset the watcher
func (w *Watcher) GetElapsedTime() time.Duration //get the elapsed time of function execution

例子:

package main

import (
    "fmt"
    "github.com/duke-git/lancet/function"
)

func main() {
    w := &function.Watcher{}
    w.Start()

    longRunningTask()

    fmt.Println(w.excuting) //true

    w.Stop()

    eapsedTime := w.GetElapsedTime().Milliseconds()
    fmt.Println(eapsedTime)

    w.Reset()

    fmt.Println(w.excuting) //false

    fmt.Println(w.startTime) //0
    fmt.Println(w.stopTime) //0
}

func longRunningTask() {
    var slice []int64
    for i := 0; i < 10000000; i++ {
        slice = append(slice, int64(i))
    }
}