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


julia> keytype(Dict{String, Int})

This example demonstrates the usage of keytype to retrieve the key type of a Dict associative collection type. The keytype function returns the key type of the collection.

julia> keytype(Set{Float64})

In this example, keytype is used to obtain the key type of a Set collection, which is Float64.

julia> keytype(Tuple{Symbol, Int})

Here, keytype is applied to a Tuple collection type, and it returns the key type as Symbol.

Common mistake example:

julia> keytype(Vector{Int})
ERROR: MethodError: no method matching keytype(::Type{Array{Int64,1}})

In this example, keytype is mistakenly used on an array type, which results in an error. keytype is specifically used for associative collections and not arrays.

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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