懒汉式单例

非线程安全的懒汉

在多线程下可能会创建多次对象

package single
import "sync"
var lm *lazyMan
type lazyMan struct {
    age int
    mux sync.RWMutex
}
func GetLazyMan() *lazyMan {
    if lm == nil {
        lm = new(lazyMan)
    }
    return lm
}
func (lm *lazyMan) IncrementAge() {
    lm.mux.Lock()
    defer lm.mux.Unlock()
    lm.age++
}
func (lm *lazyMan) GetAge() int {
    lm.mux.RLock()
    defer lm.mux.RUnlock()
    return lm.age
}

线程安全的懒汉

// 双重检测锁(DCL懒汉式)
// 避免每次加锁，提高代码效率
func GetLazyManSync() *lazyMan {
    if lm == nil {
        lock.Lock()
        defer lock.Unlock()
        if lm == nil {
            lm = new(lazyMan)
        }
    }
    return lm
}

var once sync.Once
// sync.Once实现
func GetLazyManOnce() *lazyMan {
    once.Do(func() {
        lm = new(lazyMan)
    })
    return lm
}