> For the complete documentation index, see [llms.txt](https://freeioe.gitbook.io/doc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://freeioe.gitbook.io/doc/reference/app/utils/calc.md).

# 数据订阅计算

***

## 数据订阅计算工具模块

> \*\*\* API\_VER: 5 \*\*\*

本模块封装了数据订阅计算所需的基础代码和逻辑，帮助用户快速开发数据交叉计算应用

1. 确保进行计算时，数据点的数据是就绪的
2. 确保当数据变化时，才进行计算
3. 支持周期性回调

### initialize

模块实例构造函数

**函数原型**

```lua
function calc:initialize(sys, api, logger)
```

**参数**

* sys 系统接口
* api 应用接口
* logger 日志接口

**示例代码**

```lua
local app_calc = require 'app.utils.calc'

local calc = app_calc:new(self._sys, self._api, self._logger)
```

### add

增加交叉计算单元

**函数原型**

```lua
function calc:add(name, inputs, trigger_cb, cycle_time)
```

**参数**

* name 单元名称
* inputs 设备数据输入项列表。
* trigger\_cb 当设备数据输入项全部就绪或有变更时回调此函数，参数为数据当前值，顺序为inputs数组的顺序
* cycle\_time 周期回调时间(如不指定，则不进行周期回调),单位是秒

**示例代码**

```lua

local inputs = {
    {sn='device_sn', input='Va', prop='value', default=0},
    {sn='device_sn', input='Vb', prop='value', default=0}
}

calc:add('example_calc_unit', inputs, function(Va, Vb)
    --- Your code here
end)
```

### remove

删除交叉计算单元

**函数原型**

```lua
function calc:remove(name)
```

删除计算单元。

**参数**

* name 单元名称

**示例代码**

```lua
calc:remove('example_calc_unit')
```

### start

添加计算单元后，应该调用此方法，让模块背后的逻辑启动运行。

**函数原型**

```lua
function calc:start(handler)
```

启动计算单元，handler是应用调用api:set\_handler时使用的对象。

### stop

停止计算单元后，所有添加的计算单元将不再被执行。

**函数原型**

```lua
function calc:stop()
```

停止计算单元。


---

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