Solidity ParseError with null
mapping (address => uint) itemsPerCreator;
if (itemsPerCreator[_creator] == null){}
Remix give me a error: ParseError: Expected primary expression.
_creator is a addres type variable. Inside the mapping each addres have a uint value.
solidity
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
|
show 6 more comments
mapping (address => uint) itemsPerCreator;
if (itemsPerCreator[_creator] == null){}
Remix give me a error: ParseError: Expected primary expression.
_creator is a addres type variable. Inside the mapping each addres have a uint value.
solidity
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
What isnull?
– goodvibration
Dec 26 '18 at 9:28
The if is inside a function. So I´m trying to evaluate if is a value inside the mapping. That mapping have one a address and a uint value. So im evaluating if the value inside the mapping is null
– Eduardo
Dec 26 '18 at 9:29
It doesn't answer my question - where have you declared auintvariable namednull?
– goodvibration
Dec 26 '18 at 9:30
null is not a variable. Is a value
– Eduardo
Dec 26 '18 at 9:31
1
Any unmapped value is actually mapped to the zero value of the given type, which in your case isuint(0), or simply0.
– goodvibration
Dec 26 '18 at 9:50
|
show 6 more comments
mapping (address => uint) itemsPerCreator;
if (itemsPerCreator[_creator] == null){}
Remix give me a error: ParseError: Expected primary expression.
_creator is a addres type variable. Inside the mapping each addres have a uint value.
solidity
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
mapping (address => uint) itemsPerCreator;
if (itemsPerCreator[_creator] == null){}
Remix give me a error: ParseError: Expected primary expression.
_creator is a addres type variable. Inside the mapping each addres have a uint value.
solidity
solidity
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
edited Dec 26 '18 at 11:14
Eduardo
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
asked Dec 26 '18 at 9:16
EduardoEduardo
2438
2438
What isnull?
– goodvibration
Dec 26 '18 at 9:28
The if is inside a function. So I´m trying to evaluate if is a value inside the mapping. That mapping have one a address and a uint value. So im evaluating if the value inside the mapping is null
– Eduardo
Dec 26 '18 at 9:29
It doesn't answer my question - where have you declared auintvariable namednull?
– goodvibration
Dec 26 '18 at 9:30
null is not a variable. Is a value
– Eduardo
Dec 26 '18 at 9:31
1
Any unmapped value is actually mapped to the zero value of the given type, which in your case isuint(0), or simply0.
– goodvibration
Dec 26 '18 at 9:50
|
show 6 more comments
What isnull?
– goodvibration
Dec 26 '18 at 9:28
The if is inside a function. So I´m trying to evaluate if is a value inside the mapping. That mapping have one a address and a uint value. So im evaluating if the value inside the mapping is null
– Eduardo
Dec 26 '18 at 9:29
It doesn't answer my question - where have you declared auintvariable namednull?
– goodvibration
Dec 26 '18 at 9:30
null is not a variable. Is a value
– Eduardo
Dec 26 '18 at 9:31
1
Any unmapped value is actually mapped to the zero value of the given type, which in your case isuint(0), or simply0.
– goodvibration
Dec 26 '18 at 9:50
What is
null?– goodvibration
Dec 26 '18 at 9:28
What is
null?– goodvibration
Dec 26 '18 at 9:28
The if is inside a function. So I´m trying to evaluate if is a value inside the mapping. That mapping have one a address and a uint value. So im evaluating if the value inside the mapping is null
– Eduardo
Dec 26 '18 at 9:29
The if is inside a function. So I´m trying to evaluate if is a value inside the mapping. That mapping have one a address and a uint value. So im evaluating if the value inside the mapping is null
– Eduardo
Dec 26 '18 at 9:29
It doesn't answer my question - where have you declared a
uint variable named null?– goodvibration
Dec 26 '18 at 9:30
It doesn't answer my question - where have you declared a
uint variable named null?– goodvibration
Dec 26 '18 at 9:30
null is not a variable. Is a value
– Eduardo
Dec 26 '18 at 9:31
null is not a variable. Is a value
– Eduardo
Dec 26 '18 at 9:31
1
1
Any unmapped value is actually mapped to the zero value of the given type, which in your case is
uint(0), or simply 0.– goodvibration
Dec 26 '18 at 9:50
Any unmapped value is actually mapped to the zero value of the given type, which in your case is
uint(0), or simply 0.– goodvibration
Dec 26 '18 at 9:50
|
show 6 more comments
1 Answer
1
active
oldest
votes
You are getting this error because there is nothing like null or undefined in solidity. An uint initializes with 0.
So, to check the zero-state of value(either default or intentionally updated) to the corresponding key in your mapping, you should write it as:
if (itemsPerCreator[_creator] == 0){}
As per the Solidity documentation:
A variable which is declared will have an initial default value whose
byte-representation is all zeros. The “default values” of variables
are the typical “zero-state” of whatever the type is. For example, the
default value for a bool is false. The default value for the uint or
int types is 0. For statically-sized arrays and bytes1 to bytes32,
each individual element will be initialized to the default value
corresponding to its type. Finally, for dynamically-sized arrays,
bytes and string, the default value is an empty array or string.
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
The partto check the non-existence of value to the corresponding key in your mappingis wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.
– goodvibration
Dec 26 '18 at 10:18
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
add a comment |
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1 Answer
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1 Answer
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votes
You are getting this error because there is nothing like null or undefined in solidity. An uint initializes with 0.
So, to check the zero-state of value(either default or intentionally updated) to the corresponding key in your mapping, you should write it as:
if (itemsPerCreator[_creator] == 0){}
As per the Solidity documentation:
A variable which is declared will have an initial default value whose
byte-representation is all zeros. The “default values” of variables
are the typical “zero-state” of whatever the type is. For example, the
default value for a bool is false. The default value for the uint or
int types is 0. For statically-sized arrays and bytes1 to bytes32,
each individual element will be initialized to the default value
corresponding to its type. Finally, for dynamically-sized arrays,
bytes and string, the default value is an empty array or string.
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
The partto check the non-existence of value to the corresponding key in your mappingis wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.
– goodvibration
Dec 26 '18 at 10:18
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
add a comment |
You are getting this error because there is nothing like null or undefined in solidity. An uint initializes with 0.
So, to check the zero-state of value(either default or intentionally updated) to the corresponding key in your mapping, you should write it as:
if (itemsPerCreator[_creator] == 0){}
As per the Solidity documentation:
A variable which is declared will have an initial default value whose
byte-representation is all zeros. The “default values” of variables
are the typical “zero-state” of whatever the type is. For example, the
default value for a bool is false. The default value for the uint or
int types is 0. For statically-sized arrays and bytes1 to bytes32,
each individual element will be initialized to the default value
corresponding to its type. Finally, for dynamically-sized arrays,
bytes and string, the default value is an empty array or string.
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
The partto check the non-existence of value to the corresponding key in your mappingis wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.
– goodvibration
Dec 26 '18 at 10:18
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
add a comment |
You are getting this error because there is nothing like null or undefined in solidity. An uint initializes with 0.
So, to check the zero-state of value(either default or intentionally updated) to the corresponding key in your mapping, you should write it as:
if (itemsPerCreator[_creator] == 0){}
As per the Solidity documentation:
A variable which is declared will have an initial default value whose
byte-representation is all zeros. The “default values” of variables
are the typical “zero-state” of whatever the type is. For example, the
default value for a bool is false. The default value for the uint or
int types is 0. For statically-sized arrays and bytes1 to bytes32,
each individual element will be initialized to the default value
corresponding to its type. Finally, for dynamically-sized arrays,
bytes and string, the default value is an empty array or string.
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
You are getting this error because there is nothing like null or undefined in solidity. An uint initializes with 0.
So, to check the zero-state of value(either default or intentionally updated) to the corresponding key in your mapping, you should write it as:
if (itemsPerCreator[_creator] == 0){}
As per the Solidity documentation:
A variable which is declared will have an initial default value whose
byte-representation is all zeros. The “default values” of variables
are the typical “zero-state” of whatever the type is. For example, the
default value for a bool is false. The default value for the uint or
int types is 0. For statically-sized arrays and bytes1 to bytes32,
each individual element will be initialized to the default value
corresponding to its type. Finally, for dynamically-sized arrays,
bytes and string, the default value is an empty array or string.
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
edited Dec 26 '18 at 10:26
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
answered Dec 26 '18 at 10:09
AniketAniket
2,0471633
2,0471633
The partto check the non-existence of value to the corresponding key in your mappingis wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.
– goodvibration
Dec 26 '18 at 10:18
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
add a comment |
The partto check the non-existence of value to the corresponding key in your mappingis wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.
– goodvibration
Dec 26 '18 at 10:18
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
The part
to check the non-existence of value to the corresponding key in your mapping is wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.– goodvibration
Dec 26 '18 at 10:18
The part
to check the non-existence of value to the corresponding key in your mapping is wrong. A value exists, and it is 0. In addition to that, any key mapped to 0 can also be added in an explicit manner.– goodvibration
Dec 26 '18 at 10:18
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
@goodvibration You're right, answer updated.
– Aniket
Dec 26 '18 at 10:28
add a comment |
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What is
null?– goodvibration
Dec 26 '18 at 9:28
The if is inside a function. So I´m trying to evaluate if is a value inside the mapping. That mapping have one a address and a uint value. So im evaluating if the value inside the mapping is null
– Eduardo
Dec 26 '18 at 9:29
It doesn't answer my question - where have you declared a
uintvariable namednull?– goodvibration
Dec 26 '18 at 9:30
null is not a variable. Is a value
– Eduardo
Dec 26 '18 at 9:31
1
Any unmapped value is actually mapped to the zero value of the given type, which in your case is
uint(0), or simply0.– goodvibration
Dec 26 '18 at 9:50