[英]Typescript Discriminated Unions typesafety not working on child object?
我正在使用 Typescript 4 试图创建一个对象,该对象的属性使用可区分联合,但类型安全似乎不起作用?
export enum StageType {
PULL = 'pull',
FILTER = 'filter',
}
export enum StageMetricProperty {
IMPORTED = 'imported',
SKIPPED = 'skipped',
PIPED = 'piped',
ERRORS = 'errors',
PROCESSED = 'processed',
SENT = 'sent',
SAVED = 'saved',
}
// Pull stage metrics
export interface PullMetrics {
[StageMetricProperty.IMPORTED]?: number;
[StageMetricProperty.PIPED]?: number;
[StageMetricProperty.ERRORS]?: number;
}
export interface PullReportStage {
type: StageType.PULL;
name: string;
args: string[];
status: StageStatus;
errors: string[];
metrics: PullMetrics;
}
// Filter Stage Metrics
export interface FilterMetrics {
[StageMetricProperty.SKIPPED]?: number;
[StageMetricProperty.PIPED]?: number;
[StageMetricProperty.ERRORS]?: number;
}
export interface FilterReportStage {
type: StageType.FILTER;
name: string;
args: string[];
status: StageStatus;
errors: string[];
metrics: FilterMetrics;
}
export type ReportStage =
| PullReportStage
| FilterReportStage;
使用上述定义,我尝试创建我的 FilterReportStage 对象(如下),但 Typescript 从不报告FilterReportStage.metrics
属性内的对象的任何错误,尽管它确实正确报告了顶级metric: FilterMetrics
错误metric: FilterMetrics
对象?
const metric: FilterMetrics = {
[StageMetricProperty.IMPORTED]: 123, // <-- Correctly parsed as invalid (as expected).
[StageMetricProperty.PIPED]: 123, // <-- Valid
};
const sample = {
type: StageType.FILTER,
name: 'utils:command',
args: [],
errors: [],
metrics: {
[StageMetricProperty.IMPORTED]: 123, // <-- Invalid, Typescript does not report aby errors.
[StageMetricProperty.PIPED]: 123, // <-- Valid
} as FilterMetrics,
status: StageStatus.PENDING
} as FilterReportStage;
有没有人能够指导我为什么会发生这种情况?
当你使用类型断言(例如, as FilterMetrics
)时,你告诉打字稿“我比你更了解,所以不要在这里检查我的工作。假设它是我说的类型”。 所以既然你告诉打字稿不要检查你的工作,它就不会。
如果您想要类型检查,则使用标准类型(例如: FilterReportStage
),而不是类型断言:
const sample: FilterReportStage = {
type: StageType.FILTER,
name: 'utils:command',
args: [],
errors: [],
metrics: {
[StageMetricProperty.IMPORTED]: 123, // <--- it points out the error here
[StageMetricProperty.PIPED]: 123,
},
status: StageStatus.PENDING
};
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