英文:
julia - Why do single functions in vector passed as arguments not work
问题
我有一个演示，演示如何将函数作为参数传递给另一个函数。但并非在所有情况下都有效。
问题在于我得到了：::Vector{typeof(is_valid_wallet_address)} 而不是 Vector{Function}。
function validate(data::NamedTuple, field::Symbol, validators::Vector{Function})for validator in validatorsvalidator(data[field])endendfunction is_valid_wallet_address(address)# 钱包地址的验证逻辑endfunction is_valid_wallet_signature(signature)# 钱包签名的验证逻辑enddata = (wallet_address="123456789", wallet_signature="abcdef")# 正常工作validate(data, :wallet_address, [is_valid_wallet_address, is_valid_wallet_signature])# 不起作用validate(data, :wallet_address, [is_valid_wallet_address])validate(data, :wallet_address, [is_valid_wallet_address, is_valid_wallet_address])
希望这对你有所帮助。
英文:
I have a demo here of passing functions as parameters to another function. But its not working in all cases.
The issue is im getting: ::Vector{typeof(is_valid_wallet_address)} instead of Vector{Function}
function validate(data::NamedTuple, field::Symbol, validators::Vector{Function})for validator in validatorsvalidator(data[field])endendfunction is_valid_wallet_address(address)# Validation logic for wallet addressendfunction is_valid_wallet_signature(signature)# Validation logic for wallet signatureenddata = (wallet_address="123456789", wallet_signature="abcdef")# worksvalidate(data, :wallet_address, [is_valid_wallet_address, is_valid_wallet_signature])# doesn't workvalidate(data, :wallet_address, [is_valid_wallet_address])validate(data, :wallet_address, [is_valid_wallet_address, is_valid_wallet_address])
答案1
得分: 2
这是与协变/逆变/不变子类型相关的相当常见的混淆。Julia 使用不变子类型的概念。一个很好的参考是：https://docs.julialang.org/en/v1/manual/types/#man-parametric-composite-types。
要克服这个困难，可以定义函数validate，使其接受任何Function的子类型，然后所有的调用都会按预期工作：
function validate(data::NamedTuple, field::Symbol, validators::Vector{<:Function})for validator in validatorsvalidator(data[field])endend
请注意<:在Function之前。
英文:
This is a rather common confusion related to contra-variant/covariant/invariant subtypes. Julia goes with the invariant subtyping idea. A good reference is: https://docs.julialang.org/en/v1/manual/types/#man-parametric-composite-types.
To get over this difficulty, the function validate can be defined to take any subtype of Function and then all the calls work as expected:
function validate(data::NamedTuple, field::Symbol, validators::Vector{<:Function})for validator in validatorsvalidator(data[field])endend
Note the <: before Function.
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