[](https://github.com/prettier/prettier)
# About
This package contains basic **calculating fields**, types and providers for it. Calculating field is an **abstraction which provides you formalized calculations upon not formalized source**.
# Types
## **SafeCF**
Mapper from Source to Result types, null will be returned in
case of runtime error
```typescript
type SafeCF = (source: Source) => Result | null;
```
## **UnsafeCF**
Mapper from unknown type to Result type, exception can be
thrown hypothetically
```typescript
type UnsafeCF = (source: unknown) => Result;
```
## **Guarantor**
Function which takes UnsafeCF and returns SafeCF
```typescript
type Guarantor = (
unsafeCF: UnsafeCF
) => SafeCF;
```
# Functions
## **blank**
Blank calculating field which does nothing
with source and just returns it (with additional
logic possibly)
```typescript
type Args = {
/**
* Additional logic will be used when this calculating
* field is applied
*/
additionalLogic?: () => void;
};
type Signature = ({ additionalLogic }: Args) => SafeCF;
```
## **defaultValue**
Calculating field which returns given value
in case of source was undefined and/or null
and returns source otherwise
```typescript
type Args = {
/**
* Value will be returned if source is undefined and/or null
* (only for undefined by default)
*/
value: T;
/**
* If this flag is set to true, value will be returned also
* in case of source is null
*/
replaceNullValues?: boolean;
};
type Signature = ({
value,
replaceNullValues = false
}: Args) => SafeCF<
SupposedSourceValue,
SupposedSourceValue | Value
>;
```
## **fixed**
Calculating field which always returns
given value
```typescript
type Args = {
/**
* Value will be returned in any case
*/
value: T;
};
type Signature = ({ value }: Args) => SafeCF;
```
## **getGuarantor**
Function which returns guarantor to make
SafeCF from UnsafeCF
```typescript
type Args = {
/**
* This function will be used to check if source
* is of required type
*/
typeCheck: (target: any) => boolean;
/**
* This function will be used to map source of
* unknown type to required type if typeCheck
* function returned false
*/
sourceTypeMapper?: (target: unknown) => Source | null;
/**
* Custom exception handler
*/
exceptionHandler?: (exception: Error) => void;
};
type Signature = ({
typeCheck,
sourceTypeMapper,
exceptionHandler
}: Args) => Guarantor;
```
## **pipe**
Function which takes array of SafeCFs and
returns one SafeCF which stores given
calculating fields applying logic according
to their order in argument array
```typescript
type Args = {
/**
* This function will be used to check if source
* is of required type
*/
typeCheck: (target: any) => boolean;
/**
* This function will be used to map source of
* unknown type to required type if typeCheck
* function returned false
*/
sourceTypeMapper?: (target: unknown) => Source | null;
/**
* Custom exception handler
*/
exceptionHandler?: (exception: Error) => void;
};
type Signature = ({
typeCheck,
sourceTypeMapper,
exceptionHandler
}: Args) => Guarantor;
```
## **selector**
Function which applies one of two given
calculating fields according to source
check result
```typescript
type Args = {
/**
* Check will be used to select positive or
* negative case CF
*/
check: (source: Source) => boolean;
/**
* Calculating field will be applied if
* check returned true
*/
positiveCase: SafeCF;
/**
* Calculating field will be applied if
* check returned false
*/
negativeCase: SafeCF;
};
type Signature = ({
check,
negativeCase,
positiveCase
}: Args) => SafeCF<
Source,
PositiveCaseResult | NegativeCaseResult
>;
```
---
_Source: https://npm.io/package/thesmo-calc-fields-base · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._
