[英]Typescript how to assign generics to generic variable field
How do I correctly assign a generic class field to a generic local field?如何将通用类字段正确分配给通用本地字段?
For example I have this generic interface implemented in a generic class例如,我在通用类中实现了这个通用接口
export interface TableBoxProps<T> {
getDataSource: <T> () => T[];
}
class Container<T> extends React.Component<TableBoxProps<T>, any>{ ... }
and somewhere I have a function where I want to get an entry from the datasource eg like this在某处我有一个函数,我想从数据源中获取一个条目,例如像这样
private onCellClick = (row: number, column: number) => {
let entity:T = this.props.getDataSource()[row]; // error
}
I get the error with the above我收到上述错误
[ts] Type '{}' is not assignable to type 'T'
What do I have to change that I can use let entity:T
?我必须改变什么才能使用
let entity:T
? It works fine with the type any
, but I don't want to do that.它适用于
any
类型,但我不想这样做。
Your definition of TableBoxProps<T>
is wrong.您对
TableBoxProps<T>
定义是错误的。 In getDataSource: <T> () => T[];
在
getDataSource: <T> () => T[];
, the <T>
shouldn't be here as it declares another generic type T
that shadows the TableBoxProps<T>
. ,
<T>
不应该在这里,因为它声明了另一个TableBoxProps<T>
泛型类型T
You actually declared a generic function in a generic interface.您实际上在泛型接口中声明了泛型函数。
What you have written is equal to:您所写的内容等于:
export interface TableBoxProps<T1> {
getDataSource: <T2> () => T2[];
}
And correct solution should be正确的解决方案应该是
export interface TableBoxProps<T> {
getDataSource: () => T[];
}
This is caused because this.props.getDataSource()[row]
is of type {}
.这是因为
this.props.getDataSource()[row]
的类型是{}
。 You need to cast it to T:您需要将其转换为 T:
let entity: T = (this.props.getDataSource()[row] as T);
You need to use as T
rather than <T>
because you are using React with JSX.您需要使用
as T
而不是<T>
因为您使用的是带有 JSX 的 React。
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