Supplying implicit argument EXPLICITLY
I have a function like this:
case class SomeCaseClass(i: Int)
def func[T: Manifest](someArg: Int)(implicit i: String) = {
SomeCaseClass(2)
}
I need to call func and supply i explicitly
but when I call func[SomeCaseClass](2)("hello"), I get:
error: not enough arguments for method func: (implicit evidence$1:
Manifest[ScalaFiddle.this.SomeCaseClass], implicit i:
String)ScalaFiddle.this.SomeCaseClass. Unspecified value parameter i.
funcSomeCaseClass("hello")
Any way to do it without changing the function's signature?
scala
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
add a comment |
I have a function like this:
case class SomeCaseClass(i: Int)
def func[T: Manifest](someArg: Int)(implicit i: String) = {
SomeCaseClass(2)
}
I need to call func and supply i explicitly
but when I call func[SomeCaseClass](2)("hello"), I get:
error: not enough arguments for method func: (implicit evidence$1:
Manifest[ScalaFiddle.this.SomeCaseClass], implicit i:
String)ScalaFiddle.this.SomeCaseClass. Unspecified value parameter i.
funcSomeCaseClass("hello")
Any way to do it without changing the function's signature?
scala
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
Do you have the real signature (assuming this is a simplified example)? What is the manifest being used for?
– Thilo
Nov 22 '18 at 12:06
In the actual case, the function callsjValue.extract[T]oforg.json4s.ExtractableJsonAstNode. This function's signature isdef extract[A](implicit formats: Formats, mf: scala.reflect.Manifest[A]): A. In any case, this is part of out infrastructure code, and I am very reluctant to change it.
– Barak BN
Nov 22 '18 at 12:12
1
As a side note, having an implicitstringis not a great idea... although I realize you may have simplified the type for the question.
– Lasf
Nov 22 '18 at 13:28
add a comment |
I have a function like this:
case class SomeCaseClass(i: Int)
def func[T: Manifest](someArg: Int)(implicit i: String) = {
SomeCaseClass(2)
}
I need to call func and supply i explicitly
but when I call func[SomeCaseClass](2)("hello"), I get:
error: not enough arguments for method func: (implicit evidence$1:
Manifest[ScalaFiddle.this.SomeCaseClass], implicit i:
String)ScalaFiddle.this.SomeCaseClass. Unspecified value parameter i.
funcSomeCaseClass("hello")
Any way to do it without changing the function's signature?
scala
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
I have a function like this:
case class SomeCaseClass(i: Int)
def func[T: Manifest](someArg: Int)(implicit i: String) = {
SomeCaseClass(2)
}
I need to call func and supply i explicitly
but when I call func[SomeCaseClass](2)("hello"), I get:
error: not enough arguments for method func: (implicit evidence$1:
Manifest[ScalaFiddle.this.SomeCaseClass], implicit i:
String)ScalaFiddle.this.SomeCaseClass. Unspecified value parameter i.
funcSomeCaseClass("hello")
Any way to do it without changing the function's signature?
scala
scala
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
asked Nov 22 '18 at 11:59
Barak BNBarak BN
1418
1418
Do you have the real signature (assuming this is a simplified example)? What is the manifest being used for?
– Thilo
Nov 22 '18 at 12:06
In the actual case, the function callsjValue.extract[T]oforg.json4s.ExtractableJsonAstNode. This function's signature isdef extract[A](implicit formats: Formats, mf: scala.reflect.Manifest[A]): A. In any case, this is part of out infrastructure code, and I am very reluctant to change it.
– Barak BN
Nov 22 '18 at 12:12
1
As a side note, having an implicitstringis not a great idea... although I realize you may have simplified the type for the question.
– Lasf
Nov 22 '18 at 13:28
add a comment |
Do you have the real signature (assuming this is a simplified example)? What is the manifest being used for?
– Thilo
Nov 22 '18 at 12:06
In the actual case, the function callsjValue.extract[T]oforg.json4s.ExtractableJsonAstNode. This function's signature isdef extract[A](implicit formats: Formats, mf: scala.reflect.Manifest[A]): A. In any case, this is part of out infrastructure code, and I am very reluctant to change it.
– Barak BN
Nov 22 '18 at 12:12
1
As a side note, having an implicitstringis not a great idea... although I realize you may have simplified the type for the question.
– Lasf
Nov 22 '18 at 13:28
Do you have the real signature (assuming this is a simplified example)? What is the manifest being used for?
– Thilo
Nov 22 '18 at 12:06
Do you have the real signature (assuming this is a simplified example)? What is the manifest being used for?
– Thilo
Nov 22 '18 at 12:06
In the actual case, the function calls
jValue.extract[T] of org.json4s.ExtractableJsonAstNode. This function's signature is def extract[A](implicit formats: Formats, mf: scala.reflect.Manifest[A]): A. In any case, this is part of out infrastructure code, and I am very reluctant to change it.– Barak BN
Nov 22 '18 at 12:12
In the actual case, the function calls
jValue.extract[T] of org.json4s.ExtractableJsonAstNode. This function's signature is def extract[A](implicit formats: Formats, mf: scala.reflect.Manifest[A]): A. In any case, this is part of out infrastructure code, and I am very reluctant to change it.– Barak BN
Nov 22 '18 at 12:12
1
1
As a side note, having an implicit
string is not a great idea... although I realize you may have simplified the type for the question.– Lasf
Nov 22 '18 at 13:28
As a side note, having an implicit
string is not a great idea... although I realize you may have simplified the type for the question.– Lasf
Nov 22 '18 at 13:28
add a comment |
2 Answers
2
active
oldest
votes
You need to give all implicit parameters explicitly if you give any, and T: Manifest means there is an additional implicit parameter.
Happily, implicitly method will summon the implicit which the compiler would have supplied:
func[SomeCaseClass](2)(implicitly, "hello") // inferred to implicitly[Manifest[SomeCaseClass]]
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
No, you shouldn't, it's inPredef. Do you get an error withimplicitly[Manifest[SomeCaseClass]]? If yes, what is the error?
– Alexey Romanov
Nov 22 '18 at 12:34
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
1
There's noCanBuildFrominvolved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.
– Alexey Romanov
Nov 22 '18 at 12:38
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
add a comment |
When I define the method func in my scala REPL, I am finding the output as:
func: [T](someArg: Int)(implicit evidence$1: Manifest[T], implicit i: String)SomeCaseClass
In other words, the same code can also be written as:
def func1[T](someArg: Int)(implicit manifest: Manifest[T], i: String) = {
SomeCaseClass(2)
}
It is described here as well.
So in the above code, we can see that the implicit section now have two parameters, not the only String. And you need to provide all the params of the implicit section in case you want to fill them explicitly. If you're providing just one it will throw a compilation error.
Hence your method func can be called through the below code:
func(2)(Manifest.classType(classOf[SomeCaseClass]), "hello")
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You need to give all implicit parameters explicitly if you give any, and T: Manifest means there is an additional implicit parameter.
Happily, implicitly method will summon the implicit which the compiler would have supplied:
func[SomeCaseClass](2)(implicitly, "hello") // inferred to implicitly[Manifest[SomeCaseClass]]
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
No, you shouldn't, it's inPredef. Do you get an error withimplicitly[Manifest[SomeCaseClass]]? If yes, what is the error?
– Alexey Romanov
Nov 22 '18 at 12:34
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
1
There's noCanBuildFrominvolved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.
– Alexey Romanov
Nov 22 '18 at 12:38
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
add a comment |
You need to give all implicit parameters explicitly if you give any, and T: Manifest means there is an additional implicit parameter.
Happily, implicitly method will summon the implicit which the compiler would have supplied:
func[SomeCaseClass](2)(implicitly, "hello") // inferred to implicitly[Manifest[SomeCaseClass]]
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
No, you shouldn't, it's inPredef. Do you get an error withimplicitly[Manifest[SomeCaseClass]]? If yes, what is the error?
– Alexey Romanov
Nov 22 '18 at 12:34
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
1
There's noCanBuildFrominvolved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.
– Alexey Romanov
Nov 22 '18 at 12:38
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
add a comment |
You need to give all implicit parameters explicitly if you give any, and T: Manifest means there is an additional implicit parameter.
Happily, implicitly method will summon the implicit which the compiler would have supplied:
func[SomeCaseClass](2)(implicitly, "hello") // inferred to implicitly[Manifest[SomeCaseClass]]
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
You need to give all implicit parameters explicitly if you give any, and T: Manifest means there is an additional implicit parameter.
Happily, implicitly method will summon the implicit which the compiler would have supplied:
func[SomeCaseClass](2)(implicitly, "hello") // inferred to implicitly[Manifest[SomeCaseClass]]
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
answered Nov 22 '18 at 12:22
Alexey RomanovAlexey Romanov
106k25210351
106k25210351
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
No, you shouldn't, it's inPredef. Do you get an error withimplicitly[Manifest[SomeCaseClass]]? If yes, what is the error?
– Alexey Romanov
Nov 22 '18 at 12:34
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
1
There's noCanBuildFrominvolved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.
– Alexey Romanov
Nov 22 '18 at 12:38
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
add a comment |
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
No, you shouldn't, it's inPredef. Do you get an error withimplicitly[Manifest[SomeCaseClass]]? If yes, what is the error?
– Alexey Romanov
Nov 22 '18 at 12:34
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
1
There's noCanBuildFrominvolved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.
– Alexey Romanov
Nov 22 '18 at 12:38
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
should i need to import anything here ? i'm getting compiler error and my scala version is 2.11
– Balaji Reddy
Nov 22 '18 at 12:29
No, you shouldn't, it's in
Predef. Do you get an error with implicitly[Manifest[SomeCaseClass]]? If yes, what is the error?– Alexey Romanov
Nov 22 '18 at 12:34
No, you shouldn't, it's in
Predef. Do you get an error with implicitly[Manifest[SomeCaseClass]]? If yes, what is the error?– Alexey Romanov
Nov 22 '18 at 12:34
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
Type mismatch, expected: Manifest[SomeCaseClass], actual: CanBuildFrom[String, Char, String]
– Balaji Reddy
Nov 22 '18 at 12:36
1
1
There's no
CanBuildFrom involved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.– Alexey Romanov
Nov 22 '18 at 12:38
There's no
CanBuildFrom involved in your example code. Obviously if you have different types there you'll need to adjust. You can see it working at scalafiddle.io/sf/EYro2yQ/0.– Alexey Romanov
Nov 22 '18 at 12:38
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
i'm not really sure why i'm getting this error. but this is not stopping me from running the code and getting the result...
– Balaji Reddy
Nov 22 '18 at 12:49
add a comment |
When I define the method func in my scala REPL, I am finding the output as:
func: [T](someArg: Int)(implicit evidence$1: Manifest[T], implicit i: String)SomeCaseClass
In other words, the same code can also be written as:
def func1[T](someArg: Int)(implicit manifest: Manifest[T], i: String) = {
SomeCaseClass(2)
}
It is described here as well.
So in the above code, we can see that the implicit section now have two parameters, not the only String. And you need to provide all the params of the implicit section in case you want to fill them explicitly. If you're providing just one it will throw a compilation error.
Hence your method func can be called through the below code:
func(2)(Manifest.classType(classOf[SomeCaseClass]), "hello")
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
add a comment |
When I define the method func in my scala REPL, I am finding the output as:
func: [T](someArg: Int)(implicit evidence$1: Manifest[T], implicit i: String)SomeCaseClass
In other words, the same code can also be written as:
def func1[T](someArg: Int)(implicit manifest: Manifest[T], i: String) = {
SomeCaseClass(2)
}
It is described here as well.
So in the above code, we can see that the implicit section now have two parameters, not the only String. And you need to provide all the params of the implicit section in case you want to fill them explicitly. If you're providing just one it will throw a compilation error.
Hence your method func can be called through the below code:
func(2)(Manifest.classType(classOf[SomeCaseClass]), "hello")
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
add a comment |
When I define the method func in my scala REPL, I am finding the output as:
func: [T](someArg: Int)(implicit evidence$1: Manifest[T], implicit i: String)SomeCaseClass
In other words, the same code can also be written as:
def func1[T](someArg: Int)(implicit manifest: Manifest[T], i: String) = {
SomeCaseClass(2)
}
It is described here as well.
So in the above code, we can see that the implicit section now have two parameters, not the only String. And you need to provide all the params of the implicit section in case you want to fill them explicitly. If you're providing just one it will throw a compilation error.
Hence your method func can be called through the below code:
func(2)(Manifest.classType(classOf[SomeCaseClass]), "hello")
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
When I define the method func in my scala REPL, I am finding the output as:
func: [T](someArg: Int)(implicit evidence$1: Manifest[T], implicit i: String)SomeCaseClass
In other words, the same code can also be written as:
def func1[T](someArg: Int)(implicit manifest: Manifest[T], i: String) = {
SomeCaseClass(2)
}
It is described here as well.
So in the above code, we can see that the implicit section now have two parameters, not the only String. And you need to provide all the params of the implicit section in case you want to fill them explicitly. If you're providing just one it will throw a compilation error.
Hence your method func can be called through the below code:
func(2)(Manifest.classType(classOf[SomeCaseClass]), "hello")
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
answered Nov 22 '18 at 12:27
anuj saxenaanuj saxena
24917
24917
add a comment |
add a comment |
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Do you have the real signature (assuming this is a simplified example)? What is the manifest being used for?
– Thilo
Nov 22 '18 at 12:06
In the actual case, the function calls
jValue.extract[T]oforg.json4s.ExtractableJsonAstNode. This function's signature isdef extract[A](implicit formats: Formats, mf: scala.reflect.Manifest[A]): A. In any case, this is part of out infrastructure code, and I am very reluctant to change it.– Barak BN
Nov 22 '18 at 12:12
1
As a side note, having an implicit
stringis not a great idea... although I realize you may have simplified the type for the question.– Lasf
Nov 22 '18 at 13:28