Contrast with a similar query
In the previous inquiry about error TS2339: Property 'x' does not exist on type 'Y', the focus was on the concept of indexable type. This current scenario, however, appears to require different approaches for resolution.
Issue at Hand
interface INumberPropertySpecification__CommonParameters {
readonly type: PROPERTIES_TYPES.NUMBER; // enum
readonly numberType: NUMBER_TYPES; // enum
}
export type NumberPropertySpecification =
INumberPropertySpecification__Required |
INumberPropertySpecification__HasDefault |
INumberPropertySpecification__Optional;
The code snippet above defines the NumberPropertySpecification as a union of three possible cases:
- When the property is mandatory, users must explicitly specify
required: true.
interface INumberPropertySpecification__Required extends INumberPropertySpecification__CommonParameters {
readonly required: true;
readonly invalidValueSubstitution?: number;
}
// Example:
const requiredNumberPropertySpecification: INumberPropertySpecification__Required = {
type: PROPERTIES_TYPES.NUMBER,
numberType: NUMBER_TYPES.ANY_REAL_NUMBER,
required: true
}
- If the property has a default value and is not required, specifying
required: falseis unnecessary.
interface INumberPropertySpecification__HasDefault extends INumberPropertySpecification__CommonParameters {
readonly defaultValue: number;
}
// Example
const requiredNumberPropertySpecification: INumberPropertySpecification__HasDefault = {
type: PROPERTIES_TYPES.NUMBER,
numberType: NUMBER_TYPES.ANY_REAL_NUMBER,
default: 1
}
- For optional properties, users are required to explicitly state
required: false:
interface INumberPropertySpecification__Optional extends INumberPropertySpecification__CommonParameters {
readonly required: false;
}
// Example:
const requiredNumberPropertySpecification: INumberPropertySpecification__Optional = {
type: PROPERTIES_TYPES.NUMBER,
numberType: NUMBER_TYPES.ANY_REAL_NUMBER,
required: false
}
Error Troubleshooting
It is noted that checking
targetPropertySpecification.required === trueSimilarly, handling defaultValue (the isUndefined) warrants attention:
https://i.sstatic.net/PPe1C.png
A comparable issue arises when dealing with defaultValue, emphasizing the importance of proper error detection: