Get the value type of an associative collection type. Behaves similarly to eltype.


In the Julia programming language, the function valtype(type) is used to get the value type of an associative collection type. It behaves similarly to the eltype function.

julia> valtype(Dict{String, Int})

julia> valtype(StructArray{String, Int})

Common examples of its use:

  1. Get the value type of a Dictionary:

    julia> valtype(Dict{String, Int})

    This example returns the value type (Int64) of the dictionary type Dict{String, Int}.

  2. Get the value type of a StructArray:

    julia> valtype(StructArray{String, Int})

    It returns the value type (Int64) of the StructArray{String, Int} type.

  3. Handle generic associative collection types:
    julia> valtype(Dict{Any, Any})

    When working with generic associative collection types, such as Dict{Any, Any}, the function returns the value type as Any.

Common mistake example:

julia> valtype([1, 2, 3])
ERROR: MethodError: no method matching valtype(::Array{Int64,1})

In this example, the valtype function is applied to an array (Array{Int64,1}). However, valtype is specifically used for associative collection types like dictionaries and struct arrays, not regular arrays. Make sure to use valtype with associative collection types to avoid such errors.

See Also

BigFloat, BigInt, Dict, eltype, fieldtype, Float32, Float64, IntSet, isa, isalnum, isalpha, isascii, iseltype, isequal, isgraph, isimmutable, isinteractive, isleaftype, isnull, ispunct, isspace, issubtype, keytype, Nullable, NullException, promote_type, typeintersect, typejoin, typemax, typemin, typeof, Val, valtype,

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