Go设计模式03-建造者模式

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序

Go 设计模式实现，包含常见的设计模式实现，同时这也是极客时间-设计模式之美的笔记，源课程采用 Java 实现，本系列会采用 Go 实现
课程: 46 | 建造者模式：详解构造函数、set 方法、建造者模式三种对象创建方式
**本文代码仓库: https://github.com/mohuishou/go-design-pattern **🌟🌟🌟🌟🌟
**RoadMap: 03/22 **持续更新中，预计一周更新 2 ~ 3 种设计模式，预计到 202010 月底前更新完成
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笔记

代码实现

其实在 Golang 中对于创建类参数比较多的对象的时候，我们常见的做法是必填参数直接传递，可选参数通过传递可变的方法进行创建。
本文会先实现课程中的建造者模式，然后再实现我们常用的方式。

建造者模式

代码

通过下面可以看到，使用 Go 编写建造者模式的代码其实会很长，这些是它的一个缺点，所以如果不是参数的校验逻辑很复杂的情况下一般我们在 Go 中不会采用这种方式，而会采用后面的另外一种方式

package builder

import "fmt"

const (
	defaultMaxTotal = 10
	defaultMaxIdle  = 9
	defaultMinIdle  = 1
)

// ResourcePoolConfig resource pool
type ResourcePoolConfig struct {
	name     string
	maxTotal int
	maxIdle  int
	minIdle  int
}

// ResourcePoolConfigBuilder 用于构建 ResourcePoolConfig
type ResourcePoolConfigBuilder struct {
	name     string
	maxTotal int
	maxIdle  int
	minIdle  int
}

// SetName SetName
func (b *ResourcePoolConfigBuilder) SetName(name string) error {
	if name == "" {
		return fmt.Errorf("name can not be empty")
	}
	b.name = name
	return nil
}

// SetMinIdle SetMinIdle
func (b *ResourcePoolConfigBuilder) SetMinIdle(minIdle int) error {
	if minIdle < 0 {
		return fmt.Errorf("max tatal cannot < 0, input: %d", minIdle)
	}
	b.minIdle = minIdle
	return nil
}

// SetMaxIdle SetMaxIdle
func (b *ResourcePoolConfigBuilder) SetMaxIdle(maxIdle int) error {
	if maxIdle < 0 {
		return fmt.Errorf("max tatal cannot < 0, input: %d", maxIdle)
	}
	b.maxIdle = maxIdle
	return nil
}

// SetMaxTotal SetMaxTotal
func (b *ResourcePoolConfigBuilder) SetMaxTotal(maxTotal int) error {
	if maxTotal <= 0 {
		return fmt.Errorf("max tatal cannot <= 0, input: %d", maxTotal)
	}
	b.maxTotal = maxTotal
	return nil
}

// Build Build
func (b *ResourcePoolConfigBuilder) Build() (*ResourcePoolConfig, error) {
	if b.name == "" {
		return nil, fmt.Errorf("name can not be empty")
	}

	// 设置默认值
	if b.minIdle == 0 {
		b.minIdle = defaultMinIdle
	}

	if b.maxIdle == 0 {
		b.maxIdle = defaultMaxIdle
	}

	if b.maxTotal == 0 {
		b.maxTotal = defaultMaxTotal
	}

	if b.maxTotal < b.maxIdle {
		return nil, fmt.Errorf("max total(%d) cannot < max idle(%d)", b.maxTotal, b.maxIdle)
	}

	if b.minIdle > b.maxIdle {
		return nil, fmt.Errorf("max idle(%d) cannot < min idle(%d)", b.maxIdle, b.minIdle)
	}

	return &ResourcePoolConfig{
		name:     b.name,
		maxTotal: b.maxTotal,
		maxIdle:  b.maxIdle,
		minIdle:  b.minIdle,
	}, nil
}

单元测试

package builder

import (
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestResourcePoolConfigBuilder_Build(t *testing.T) {
	tests := []struct {
		name    string
		builder *ResourcePoolConfigBuilder
		want    *ResourcePoolConfig
		wantErr bool
	}{
		{
			name: "name empty",
			builder: &ResourcePoolConfigBuilder{
				name:     "",
				maxTotal: 0,
			},
			want:    nil,
			wantErr: true,
		},
		{
			name: "maxIdle < minIdle",
			builder: &ResourcePoolConfigBuilder{
				name:     "test",
				maxTotal: 0,
				maxIdle:  10,
				minIdle:  20,
			},
			want:    nil,
			wantErr: true,
		},
		{
			name: "success",
			builder: &ResourcePoolConfigBuilder{
				name: "test",
			},
			want: &ResourcePoolConfig{
				name:     "test",
				maxTotal: defaultMaxTotal,
				maxIdle:  defaultMaxIdle,
				minIdle:  defaultMinIdle,
			},
			wantErr: false,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := tt.builder.Build()
			require.Equalf(t, tt.wantErr, err != nil, "Build() error = %v, wantErr %v", err, tt.wantErr)
			assert.Equal(t, tt.want, got)
		})
	}
}

Go 常用的参数传递方法

代码

package builder

import "fmt"

// ResourcePoolConfigOption option
type ResourcePoolConfigOption struct {
	maxTotal int
	maxIdle  int
	minIdle  int
}

// ResourcePoolConfigOptFunc to set option
type ResourcePoolConfigOptFunc func(option *ResourcePoolConfigOption)

// NewResourcePoolConfig NewResourcePoolConfig
func NewResourcePoolConfig(name string, opts ...ResourcePoolConfigOptFunc) (*ResourcePoolConfig, error) {
	if name == "" {
		return nil, fmt.Errorf("name can not be empty")
	}

	option := &ResourcePoolConfigOption{
		maxTotal: 10,
		maxIdle:  9,
		minIdle:  1,
	}

	for _, opt := range opts {
		opt(option)
	}

	if option.maxTotal < 0 || option.maxIdle < 0 || option.minIdle < 0 {
		return nil, fmt.Errorf("args err, option: %v", option)
	}

	if option.maxTotal < option.maxIdle || option.minIdle > option.maxIdle {
		return nil, fmt.Errorf("args err, option: %v", option)
	}

	return &ResourcePoolConfig{
		name:     name,
		maxTotal: option.maxTotal,
		maxIdle:  option.maxIdle,
		minIdle:  option.minIdle,
	}, nil
}

单元测试

package builder

import (
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestNewResourcePoolConfig(t *testing.T) {
	type args struct {
		name string
		opts []ResourcePoolConfigOptFunc
	}
	tests := []struct {
		name    string
		args    args
		want    *ResourcePoolConfig
		wantErr bool
	}{
		{
			name: "name empty",
			args: args{
				name: "",
			},
			want:    nil,
			wantErr: true,
		},
		{
			name: "success",
			args: args{
				name: "test",
				opts: []ResourcePoolConfigOptFunc{
					func(option *ResourcePoolConfigOption) {
						option.minIdle = 2
					},
				},
			},
			want: &ResourcePoolConfig{
				name:     "test",
				maxTotal: 10,
				maxIdle:  9,
				minIdle:  2,
			},
			wantErr: false,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := NewResourcePoolConfig(tt.args.name, tt.args.opts...)
			require.Equalf(t, tt.wantErr, err != nil, "error = %v, wantErr %v", err, tt.wantErr)
			assert.Equal(t, tt.want, got)
		})
	}
}