Attribute-Set Functionslib.attrset.attrByPathattrByPath :: [String] -> Any -> AttrSet
Return an attribute from within nested attribute sets.
attrPath
A list of strings representing the path through the nested attribute set
set.
default
Default value if attrPath does not resolve to an
existing value.
set
The nested attributeset to select values from.
Extracting a value from a nested attribute set 3
]]>No value at the path, instead using the default 0
]]>lib.attrsets.hasAttrByPathhasAttrByPath :: [String] -> AttrSet -> Bool
Determine if an attribute exists within a nested attribute set.
attrPath
A list of strings representing the path through the nested attribute set
set.
set
The nested attributeset to check.
A nested value does exist inside a set true
]]>lib.attrsets.setAttrByPathsetAttrByPath :: [String] -> Any -> AttrSet
Create a new attribute set with value set at the nested
attribute location specified in attrPath.
attrPath
A list of strings representing the path through the nested attribute set.
value
The value to set at the location described by
attrPath.
Creating a new nested attribute set { a = { b = 3; }; }
]]>lib.attrsets.getAttrFromPathgetAttrFromPath :: [String] -> AttrSet -> Value
Like except
without a default, and it will throw if the value doesn't exist.
attrPath
A list of strings representing the path through the nested attribute set
set.
set
The nested attribute set to find the value in.
Succesfully getting a value from an attribute set 3
]]>Throwing after failing to get a value from an attribute set error: cannot find attribute `x.y'
]]>lib.attrsets.attrValsattrVals :: [String] -> AttrSet -> [Any]
Return the specified attributes from a set. All values must exist.
nameList
The list of attributes to fetch from set. Each
attribute name must exist on the attrbitue set.
set
The set to get attribute values from.
Getting several values from an attribute set [ 1 2 3 ]
]]>Getting missing values from an attribute setlib.attrsets.attrValuesattrValues :: AttrSet -> [Any]
Get all the attribute values from an attribute set.
Provides a backwards-compatible interface of
builtins.attrValues for Nix version older than 1.8.
attrs
The attribute set.
[ 1 2 3 ]
]]>lib.attrsets.catAttrscatAttrs :: String -> AttrSet -> [Any]
Collect each attribute named `attr' from the list of attribute sets,
sets. Sets that don't contain the named attribute are
ignored.
Provides a backwards-compatible interface of
builtins.catAttrs for Nix version older than 1.9.
attr
Attribute name to select from each attribute set in
sets.
sets
The list of attribute sets to select attr from.
Collect an attribute from a list of attribute sets.
Attribute sets which don't have the attribute are ignored.
[ 1 2 ]
]]>lib.attrsets.filterAttrsfilterAttrs :: (String -> Any -> Bool) -> AttrSet -> AttrSet
Filter an attribute set by removing all attributes for which the given
predicate return false.
predString -> Any -> Bool
Predicate which returns true to include an attribute, or returns false to
exclude it.
name
The attribute's name
value
The attribute's value
Returns true to include the attribute,
false to exclude the attribute.
set
The attribute set to filter
Filtering an attributeset { foo = 1; }
]]>lib.attrsets.filterAttrsRecursivefilterAttrsRecursive :: (String -> Any -> Bool) -> AttrSet -> AttrSet
Filter an attribute set recursively by removing all attributes for which the
given predicate return false.
predString -> Any -> Bool
Predicate which returns true to include an attribute, or returns false to
exclude it.
name
The attribute's name
value
The attribute's value
Returns true to include the attribute,
false to exclude the attribute.
set
The attribute set to filter
Recursively filtering an attribute set {
levelA = {
example = "hi";
levelB = {
hello = "there";
this-one-is-present = { };
};
};
}
]]>lib.attrsets.foldAttrsfoldAttrs :: (Any -> Any -> Any) -> Any -> [AttrSets] -> Any
Apply fold function to values grouped by key.
opAny -> Any -> Any
Given a value val and a collector
col, combine the two.
val
An attribute's value
col
The result of previous op calls with other values
and nul.
nul
The null-value, the starting value.
list_of_attrs
A list of attribute sets to fold together by key.
Combining an attribute of lists in to one attribute set { a = [ 2 3 ]; b = [ 7 6 ]; }
]]>lib.attrsets.collectcollect :: (Any -> Bool) -> AttrSet -> [Any]
Recursively collect sets that verify a given predicate named
pred from the set attrs. The recursion
stops when pred returns true.
predAny -> Bool
Given an attribute's value, determine if recursion should stop.
value
The attribute set value.
attrs
The attribute set to recursively collect.
Collecting all lists from an attribute set [["b"] [1]]
]]>Collecting all attribute-sets which contain the outPath attribute name. [{ outPath = "a/"; } { outPath = "b/"; }]
]]>lib.attrsets.nameValuePairnameValuePair :: String -> Any -> AttrSet
Utility function that creates a {name, value} pair as
expected by builtins.listToAttrs.
name
The attribute name.
value
The attribute value.
Creating a name value pair { name = "some"; value = 6; }
]]>lib.attrsets.mapAttrs
Apply a function to each element in an attribute set, creating a new
attribute set.
Provides a backwards-compatible interface of
builtins.mapAttrs for Nix version older than 2.1.
fnString -> Any -> Any
Given an attribute's name and value, return a new value.
name
The name of the attribute.
value
The attribute's value.
Modifying each value of an attribute set { x = "x-foo"; y = "y-bar"; }
]]>lib.attrsets.mapAttrs'mapAttrs' :: (String -> Any -> { name = String; value = Any }) -> AttrSet -> AttrSet
Like mapAttrs, but allows the name of each attribute to
be changed in addition to the value. The applied function should return both
the new name and value as a nameValuePair.
fnString -> Any -> { name = String; value = Any }
Given an attribute's name and value, return a new
name
value pair.
name
The name of the attribute.
value
The attribute's value.
set
The attribute set to map over.
Change the name and value of each attribute of an attribute set { foo_x = "bar-a"; foo_y = "bar-b"; }
]]>lib.attrsets.mapAttrsToListmapAttrsToList :: (String -> Any -> Any) ->
AttrSet -> Any
Call fn for each attribute in the given
set and return the result in a list.
fnString -> Any -> Any
Given an attribute's name and value, return a new value.
name
The name of the attribute.
value
The attribute's value.
set
The attribute set to map over.
Combine attribute values and names in to a list [ "x=a" "y=b" ]
]]>lib.attrsets.mapAttrsRecursivemapAttrsRecursive :: ([String] > Any -> Any) -> AttrSet -> AttrSet
Like mapAttrs, except that it recursively applies
itself to attribute sets. Also, the first argument of the argument function
is a list of the names of the containing attributes.
f[ String ] -> Any -> Any
Given a list of attribute names and value, return a new value.
name_path
The list of attribute names to this value.
For example, the name_path for the
example string in the attribute set { foo
= { bar = "example"; }; } is [ "foo" "bar"
].
value
The attribute's value.
set
The attribute set to recursively map over.
A contrived example of using lib.attrsets.mapAttrsRecursive {
n = {
a = "n-a-A";
m = {
b = "n-m-b-B";
c = "n-m-c-C";
};
};
d = "d-D";
}
]]>lib.attrsets.mapAttrsRecursiveCondmapAttrsRecursiveCond :: (AttrSet -> Bool) -> ([ String ] -> Any -> Any) -> AttrSet -> AttrSet
Like mapAttrsRecursive, but it takes an additional
predicate function that tells it whether to recursive into an attribute set.
If it returns false, mapAttrsRecursiveCond does not
recurse, but does apply the map function. It is returns true, it does
recurse, and does not apply the map function.
cond(AttrSet -> Bool)
Determine if mapAttrsRecursive should recurse deeper
in to the attribute set.
attributeset
An attribute set.
f[ String ] -> Any -> Any
Given a list of attribute names and value, return a new value.
name_path
The list of attribute names to this value.
For example, the name_path for the
example string in the attribute set { foo
= { bar = "example"; }; } is [ "foo" "bar"
].
value
The attribute's value.
set
The attribute set to recursively map over.
Only convert attribute values to JSON if the containing attribute set is marked for recursion {
dorecur = {
hello = "\"there\"";
recurse = "true";
};
dontrecur = "{\"converted-to\":\"json\"}";
}
]]>lib.attrsets.genAttrsgenAttrs :: [ String ] -> (String -> Any) -> AttrSet
Generate an attribute set by mapping a function over a list of attribute
names.
names
Names of values in the resulting attribute set.
fString -> Any
Takes the name of the attribute and return the attribute's value.
name
The name of the attribute to generate a value for.
Generate an attrset based on names only { foo = "x_foo"; bar = "x_bar"; }
]]>lib.attrsets.isDerivationisDerivation :: Any -> Bool
Check whether the argument is a derivation. Any set with { type =
"derivation"; } counts as a derivation.
value
The value which is possibly a derivation.
A package is a derivation {}).ruby
=> true
]]>Anything else is not a derivation false
]]>lib.attrsets.toDerivationtoDerivation :: Path -> Derivation
Converts a store path to a fake derivation.
path
A store path to convert to a derivation.
lib.attrsets.optionalAttrsoptionalAttrs :: Bool -> AttrSet
Conditionally return an attribute set or an empty attribute set.
cond
Condition under which the as attribute set is
returned.
as
The attribute set to return if cond is true.
Return the provided attribute set when cond is true { my = "set"; }
]]>Return an empty attribute set when cond is false { }
]]>