How does Context.Value(key interface{}) interface{} work? [duplicate]
This question already has an answer here:
What exactly does .(data_type) method called/do?
2 answers
Is this casting in golang?
1 answer
I do not understand this syntax
2 answers
What does piece of code do in golang? [duplicate]
1 answer
What is this “err.(*exec.ExitError)” thing in Go code?
2 answers
Please see the below code
import (
...
"context"
...
)
type myStruct struct {
ID string
Sig string
}
mySig := myStruct{
ID: "12345678",
Sig: "Secret_Signature_Token",
}
// Setting a Value associated with a Key in Context
_ := context.WithValue(ctx, "myKey", &mySig) -- 1
//Getting the same value
value, ok := ctx.Value("myKey").(*myStruct) -- 2
Now, my question is: what is the use/meaning of .(*myStruct) in the above expression number 2
Could someone please explain the statement number 2 step by step.
go
edited Nov 27 '18 at 12:34
Flimzy
39k106597
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
marked as duplicate by Volker, JimB go
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Nov 27 '18 at 14:13
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
add a comment |
This question already has an answer here:
What exactly does .(data_type) method called/do?
2 answers
Is this casting in golang?
1 answer
I do not understand this syntax
2 answers
What does piece of code do in golang? [duplicate]
1 answer
What is this “err.(*exec.ExitError)” thing in Go code?
2 answers
Please see the below code
import (
...
"context"
...
)
type myStruct struct {
ID string
Sig string
}
mySig := myStruct{
ID: "12345678",
Sig: "Secret_Signature_Token",
}
// Setting a Value associated with a Key in Context
_ := context.WithValue(ctx, "myKey", &mySig) -- 1
//Getting the same value
value, ok := ctx.Value("myKey").(*myStruct) -- 2
Now, my question is: what is the use/meaning of .(*myStruct) in the above expression number 2
Could someone please explain the statement number 2 step by step.
go
edited Nov 27 '18 at 12:34
Flimzy
39k106597
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
marked as duplicate by Volker, JimB go
Users with the go badge can single-handedly close go questions as duplicates and reopen them as needed.
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Nov 27 '18 at 14:13
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
1
tour.golang.org/methods/15 . Redo the whole Tour.
– Volker
Nov 27 '18 at 12:11
Why are you ignoring the value returned bycontext.WithValue?
– Flimzy
Nov 27 '18 at 12:34
@Fimzy, It is a sample code snippet. :)
– Nitin Soni
Nov 27 '18 at 13:58
add a comment |
This question already has an answer here:
What exactly does .(data_type) method called/do?
2 answers
Is this casting in golang?
1 answer
I do not understand this syntax
2 answers
What does piece of code do in golang? [duplicate]
1 answer
What is this “err.(*exec.ExitError)” thing in Go code?
2 answers
Please see the below code
import (
...
"context"
...
)
type myStruct struct {
ID string
Sig string
}
mySig := myStruct{
ID: "12345678",
Sig: "Secret_Signature_Token",
}
// Setting a Value associated with a Key in Context
_ := context.WithValue(ctx, "myKey", &mySig) -- 1
//Getting the same value
value, ok := ctx.Value("myKey").(*myStruct) -- 2
Now, my question is: what is the use/meaning of .(*myStruct) in the above expression number 2
Could someone please explain the statement number 2 step by step.
go
edited Nov 27 '18 at 12:34
Flimzy
39k106597
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
This question already has an answer here:
What exactly does .(data_type) method called/do?
2 answers
Is this casting in golang?
1 answer
I do not understand this syntax
2 answers
What does piece of code do in golang? [duplicate]
1 answer
What is this “err.(*exec.ExitError)” thing in Go code?
2 answers
Please see the below code
import (
...
"context"
...
)
type myStruct struct {
ID string
Sig string
}
mySig := myStruct{
ID: "12345678",
Sig: "Secret_Signature_Token",
}
// Setting a Value associated with a Key in Context
_ := context.WithValue(ctx, "myKey", &mySig) -- 1
//Getting the same value
value, ok := ctx.Value("myKey").(*myStruct) -- 2
Now, my question is: what is the use/meaning of .(*myStruct) in the above expression number 2
Could someone please explain the statement number 2 step by step.
This question already has an answer here:
What exactly does .(data_type) method called/do?
2 answers
Is this casting in golang?
1 answer
I do not understand this syntax
2 answers
What does piece of code do in golang? [duplicate]
1 answer
What is this “err.(*exec.ExitError)” thing in Go code?
2 answers
go
go
edited Nov 27 '18 at 12:34
Flimzy
39k106597
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
edited Nov 27 '18 at 12:34
Flimzy
39k106597
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
edited Nov 27 '18 at 12:34
Flimzy
39k106597
edited Nov 27 '18 at 12:34
Flimzy
39k106597
edited Nov 27 '18 at 12:34
Flimzy
39k106597
39k106597
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
asked Nov 27 '18 at 11:47
Nitin SoniNitin Soni
13
13
marked as duplicate by Volker, JimB go
Users with the go badge can single-handedly close go questions as duplicates and reopen them as needed.
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Nov 27 '18 at 14:13
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Nov 27 '18 at 14:13
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
1
tour.golang.org/methods/15 . Redo the whole Tour.
– Volker
Nov 27 '18 at 12:11
Why are you ignoring the value returned bycontext.WithValue?
– Flimzy
Nov 27 '18 at 12:34
@Fimzy, It is a sample code snippet. :)
– Nitin Soni
Nov 27 '18 at 13:58
add a comment |
1
tour.golang.org/methods/15 . Redo the whole Tour.
– Volker
Nov 27 '18 at 12:11
Why are you ignoring the value returned bycontext.WithValue?
– Flimzy
Nov 27 '18 at 12:34
@Fimzy, It is a sample code snippet. :)
– Nitin Soni
Nov 27 '18 at 13:58
1
1
tour.golang.org/methods/15 . Redo the whole Tour.
– Volker
Nov 27 '18 at 12:11
tour.golang.org/methods/15 . Redo the whole Tour.
– Volker
Nov 27 '18 at 12:11
Why are you ignoring the value returned by
context.WithValue?– Flimzy
Nov 27 '18 at 12:34
Why are you ignoring the value returned by
context.WithValue?– Flimzy
Nov 27 '18 at 12:34
@Fimzy, It is a sample code snippet. :)
– Nitin Soni
Nov 27 '18 at 13:58
@Fimzy, It is a sample code snippet. :)
– Nitin Soni
Nov 27 '18 at 13:58
add a comment |
1 Answer
1
active
oldest
votes
ctx.Value("myKey") returns an interface. So .(*myStruct) does a type assertion to convert it to the type *myStruct. So the value on the left hand side is of type *myStruct and you can access its fields e.g. value.ID.
A version of your example can be seen here: https://play.golang.org/p/Eg0v3vuSi6y
answered Nov 27 '18 at 12:04
RafaRafa
303211
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
ctx.Value("myKey") returns an interface. So .(*myStruct) does a type assertion to convert it to the type *myStruct. So the value on the left hand side is of type *myStruct and you can access its fields e.g. value.ID.
A version of your example can be seen here: https://play.golang.org/p/Eg0v3vuSi6y
answered Nov 27 '18 at 12:04
RafaRafa
303211
add a comment |
ctx.Value("myKey") returns an interface. So .(*myStruct) does a type assertion to convert it to the type *myStruct. So the value on the left hand side is of type *myStruct and you can access its fields e.g. value.ID.
A version of your example can be seen here: https://play.golang.org/p/Eg0v3vuSi6y
answered Nov 27 '18 at 12:04
RafaRafa
303211
add a comment |
ctx.Value("myKey") returns an interface. So .(*myStruct) does a type assertion to convert it to the type *myStruct. So the value on the left hand side is of type *myStruct and you can access its fields e.g. value.ID.
A version of your example can be seen here: https://play.golang.org/p/Eg0v3vuSi6y
answered Nov 27 '18 at 12:04
RafaRafa
303211
ctx.Value("myKey") returns an interface. So .(*myStruct) does a type assertion to convert it to the type *myStruct. So the value on the left hand side is of type *myStruct and you can access its fields e.g. value.ID.
A version of your example can be seen here: https://play.golang.org/p/Eg0v3vuSi6y
answered Nov 27 '18 at 12:04
RafaRafa
303211
answered Nov 27 '18 at 12:04
RafaRafa
303211
answered Nov 27 '18 at 12:04
RafaRafa
303211
answered Nov 27 '18 at 12:04
RafaRafa
303211
303211
add a comment |
add a comment |
1
tour.golang.org/methods/15 . Redo the whole Tour.
– Volker
Nov 27 '18 at 12:11
Why are you ignoring the value returned by
context.WithValue?– Flimzy
Nov 27 '18 at 12:34
@Fimzy, It is a sample code snippet. :)
– Nitin Soni
Nov 27 '18 at 13:58