Confused by `object` type?
I am trying to come up with a type signature for a function parameter that itself is a function with a single parameter of type any object. Like this (typescript playground):
But in the strict compiler mode I am getting this error:
Argument of type '(a: { n: number; }) => void' is not assignable to parameter of type '(a: object) => void'.
Types of parameters 'a' and 'a' are incompatible.
Type 'object' is not assignable to type '{ n: number; }'.
Property 'n' is missing in type '{}'.
What am I doing wrong?
Thanks!
typescript typescript-typings
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
add a comment |
I am trying to come up with a type signature for a function parameter that itself is a function with a single parameter of type any object. Like this (typescript playground):
But in the strict compiler mode I am getting this error:
Argument of type '(a: { n: number; }) => void' is not assignable to parameter of type '(a: object) => void'.
Types of parameters 'a' and 'a' are incompatible.
Type 'object' is not assignable to type '{ n: number; }'.
Property 'n' is missing in type '{}'.
What am I doing wrong?
Thanks!
typescript typescript-typings
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
add a comment |
I am trying to come up with a type signature for a function parameter that itself is a function with a single parameter of type any object. Like this (typescript playground):
But in the strict compiler mode I am getting this error:
Argument of type '(a: { n: number; }) => void' is not assignable to parameter of type '(a: object) => void'.
Types of parameters 'a' and 'a' are incompatible.
Type 'object' is not assignable to type '{ n: number; }'.
Property 'n' is missing in type '{}'.
What am I doing wrong?
Thanks!
typescript typescript-typings
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
I am trying to come up with a type signature for a function parameter that itself is a function with a single parameter of type any object. Like this (typescript playground):
But in the strict compiler mode I am getting this error:
Argument of type '(a: { n: number; }) => void' is not assignable to parameter of type '(a: object) => void'.
Types of parameters 'a' and 'a' are incompatible.
Type 'object' is not assignable to type '{ n: number; }'.
Property 'n' is missing in type '{}'.
What am I doing wrong?
Thanks!
typescript typescript-typings
typescript typescript-typings
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
asked Nov 23 '18 at 22:40
artemaveartemave
3,37353862
3,37353862
add a comment |
add a comment |
1 Answer
1
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oldest
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bbb expects a function that can be called with any object as argument.
You're passing aaa as argument. But aaa can only be called with objects which have a property n of type number. It can't be called with any kind of object. So it's not a valid argument for bbb.
To make an analogy, bbb is like a juice bar, which needs a fruit juicer to work, i.e. a function that can take any fruit and tranform it to juice.
If you try to create a juice bar with an apple juicer (i.e. a function that can only make juice out of apples), that won't work well.
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Not sure what you exactly mean, but I guess you wantfunction bbb(fn: (a: any) => void)
– JB Nizet
Nov 24 '18 at 10:52
1
Perhaps it will be a bit better to go generic:function bbb<T extends object>(fn: (a: T) => void)- can't test it right now, though.
– Cerberus
Nov 24 '18 at 11:10
That works, thanks!
– artemave
Nov 24 '18 at 11:36
However, if I turn it to this I am still getting the same errortype Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa)
– artemave
Nov 24 '18 at 11:37
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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active
oldest
votes
bbb expects a function that can be called with any object as argument.
You're passing aaa as argument. But aaa can only be called with objects which have a property n of type number. It can't be called with any kind of object. So it's not a valid argument for bbb.
To make an analogy, bbb is like a juice bar, which needs a fruit juicer to work, i.e. a function that can take any fruit and tranform it to juice.
If you try to create a juice bar with an apple juicer (i.e. a function that can only make juice out of apples), that won't work well.
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Not sure what you exactly mean, but I guess you wantfunction bbb(fn: (a: any) => void)
– JB Nizet
Nov 24 '18 at 10:52
1
Perhaps it will be a bit better to go generic:function bbb<T extends object>(fn: (a: T) => void)- can't test it right now, though.
– Cerberus
Nov 24 '18 at 11:10
That works, thanks!
– artemave
Nov 24 '18 at 11:36
However, if I turn it to this I am still getting the same errortype Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa)
– artemave
Nov 24 '18 at 11:37
add a comment |
bbb expects a function that can be called with any object as argument.
You're passing aaa as argument. But aaa can only be called with objects which have a property n of type number. It can't be called with any kind of object. So it's not a valid argument for bbb.
To make an analogy, bbb is like a juice bar, which needs a fruit juicer to work, i.e. a function that can take any fruit and tranform it to juice.
If you try to create a juice bar with an apple juicer (i.e. a function that can only make juice out of apples), that won't work well.
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Not sure what you exactly mean, but I guess you wantfunction bbb(fn: (a: any) => void)
– JB Nizet
Nov 24 '18 at 10:52
1
Perhaps it will be a bit better to go generic:function bbb<T extends object>(fn: (a: T) => void)- can't test it right now, though.
– Cerberus
Nov 24 '18 at 11:10
That works, thanks!
– artemave
Nov 24 '18 at 11:36
However, if I turn it to this I am still getting the same errortype Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa)
– artemave
Nov 24 '18 at 11:37
add a comment |
bbb expects a function that can be called with any object as argument.
You're passing aaa as argument. But aaa can only be called with objects which have a property n of type number. It can't be called with any kind of object. So it's not a valid argument for bbb.
To make an analogy, bbb is like a juice bar, which needs a fruit juicer to work, i.e. a function that can take any fruit and tranform it to juice.
If you try to create a juice bar with an apple juicer (i.e. a function that can only make juice out of apples), that won't work well.
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
bbb expects a function that can be called with any object as argument.
You're passing aaa as argument. But aaa can only be called with objects which have a property n of type number. It can't be called with any kind of object. So it's not a valid argument for bbb.
To make an analogy, bbb is like a juice bar, which needs a fruit juicer to work, i.e. a function that can take any fruit and tranform it to juice.
If you try to create a juice bar with an apple juicer (i.e. a function that can only make juice out of apples), that won't work well.
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
edited Nov 23 '18 at 23:06
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
answered Nov 23 '18 at 22:48
JB NizetJB Nizet
536k52864997
536k52864997
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Not sure what you exactly mean, but I guess you wantfunction bbb(fn: (a: any) => void)
– JB Nizet
Nov 24 '18 at 10:52
1
Perhaps it will be a bit better to go generic:function bbb<T extends object>(fn: (a: T) => void)- can't test it right now, though.
– Cerberus
Nov 24 '18 at 11:10
That works, thanks!
– artemave
Nov 24 '18 at 11:36
However, if I turn it to this I am still getting the same errortype Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa)
– artemave
Nov 24 '18 at 11:37
add a comment |
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Not sure what you exactly mean, but I guess you wantfunction bbb(fn: (a: any) => void)
– JB Nizet
Nov 24 '18 at 10:52
1
Perhaps it will be a bit better to go generic:function bbb<T extends object>(fn: (a: T) => void)- can't test it right now, though.
– Cerberus
Nov 24 '18 at 11:10
That works, thanks!
– artemave
Nov 24 '18 at 11:36
However, if I turn it to this I am still getting the same errortype Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa)
– artemave
Nov 24 '18 at 11:37
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Thanks, that makes sense! So what is the correct way to express "accept a function with a single parameter of any object"?
– artemave
Nov 24 '18 at 10:41
Not sure what you exactly mean, but I guess you want
function bbb(fn: (a: any) => void)– JB Nizet
Nov 24 '18 at 10:52
Not sure what you exactly mean, but I guess you want
function bbb(fn: (a: any) => void)– JB Nizet
Nov 24 '18 at 10:52
1
1
Perhaps it will be a bit better to go generic:
function bbb<T extends object>(fn: (a: T) => void) - can't test it right now, though.– Cerberus
Nov 24 '18 at 11:10
Perhaps it will be a bit better to go generic:
function bbb<T extends object>(fn: (a: T) => void) - can't test it right now, though.– Cerberus
Nov 24 '18 at 11:10
That works, thanks!
– artemave
Nov 24 '18 at 11:36
That works, thanks!
– artemave
Nov 24 '18 at 11:36
However, if I turn it to this I am still getting the same error
type Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa) – artemave
Nov 24 '18 at 11:37
However, if I turn it to this I am still getting the same error
type Fn = <T extends object>(a: T) => void; function ccc(fn: Fn) { }; ccc(aaa) – artemave
Nov 24 '18 at 11:37
add a comment |
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