Documentation
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Overview ¶
Package exsync 对 sync 的扩展
Index ¶
Constants ¶
This section is empty.
Variables ¶
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Functions ¶
This section is empty.
Types ¶
type Once ¶
type Once struct {
// contains filtered or unexported fields
}
Once 是 sync.Once 的扩展实现，由于每次使用 sync.Once 都需要保存两个字段，一个是 sync.Once 的实例，一个是数据本身，这带来一些混乱 让 Once 自带数据保存，减少使用时需要定义多个字段，如果需要保存多个数据，可以使用 []interface{} 或者自定义 struct
以下是一个简单的示例： var db Once
func DB() *mysql.Client{
return db.Do(f func() interface{}{
return mysql.NewClient(...)
}).(*mysql.Client)
}
当希望处理错误，可以响应 []interface{} 或者 自定义 struct， 如果在服务或程序初始化阶段可以考虑 panic 来报告错误，如下是使用 []interface{} 的示例： var db Once
func DB() (*mysql.Client, error){
res := db.Do(f func() interface{}{
c, err:=mysql.NewClient(...)
return []interface{}{c, err}
}).([]interface{})
return res[0].(*mysql.Client), res[1].(error)
}
使用该方法需要一些取舍，它简单实用，性能无限接近 sync.Once。
func (*Once) Do ¶
func (o *Once) Do(f func() interface{}) interface{}
Do calls the function f if and only if Do is being called for the first time for this instance of Once. In other words, given
var once Once
if once.Do(f) is called multiple times, only the first call will invoke f, even if f has a different value in each invocation. A new instance of Once is required for each function to execute.
Do is intended for initialization that must be run exactly once. Since f is niladic, it may be necessary to use a function literal to capture the arguments to a function to be invoked by Do:
config.once.Do(func() { config.init(filename) })
Because no call to Do returns until the one call to f returns, if f causes Do to be called, it will deadlock.
If f panics, Do considers it to have returned; future calls of Do return without calling f.
type OncePointer ¶
type OncePointer struct {
// contains filtered or unexported fields
}
OncePointer 性能方面略好于 Once，但不会有太大改善， 在某些场景下可以使用，更推荐使用 Once
func (*OncePointer) Do ¶
func (o *OncePointer) Do(f func() unsafe.Pointer) unsafe.Pointer
Do calls the function f if and only if Do is being called for the first time for this instance of Once. In other words, given
var once Once
if once.Do(f) is called multiple times, only the first call will invoke f, even if f has a different value in each invocation. A new instance of Once is required for each function to execute.
Do is intended for initialization that must be run exactly once. Since f is niladic, it may be necessary to use a function literal to capture the arguments to a function to be invoked by Do:
config.once.Do(func() { config.init(filename) })
Because no call to Do returns until the one call to f returns, if f causes Do to be called, it will deadlock.
If f panics, Do considers it to have returned; future calls of Do return without calling f.
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