Check function exists in PowerShell module

Question

I’ve the following PowerShell script which searches in a directory for PowerShell module). All found modules will be imported and stored in a list (using the -PassThru) option. The scrip iterates over the imported modules and invokes a function defined in the module:

# Discover and import all modules
$modules = New-Object System.Collections.Generic.List[System.Management.Automation.PSModuleInfo]
$moduleFiles = Get-ChildItem -Recurse -Path "$PSScriptRoot\MyModules\" -Filter "Module.psm1"
foreach( $x in $moduleFiles ) {
    $modules.Add( (Import-Module -Name $x.FullName -PassThru) )
}

# All configuration values
$config = @{
    KeyA = "ValueA"
    KeyB = "ValueB"
    KeyC = "ValueC"
}

# Invoke 'FunctionDefinedInModule' of each module
foreach( $module in $modules ) {
    # TODO: Check function 'FunctionDefinedInModule' exists in module '$module '
    & $module FunctionDefinedInModule $config
}

Now I would like to first check if a function is defined in a module before it gets invoked. How can such a check be implemented?

The reason for adding the check if to avoid the exception thrown when calling a function which doesn’t exists:

& : The term ‘FunctionDefinedInModule’ is not recognized as the name of a cmdlet, function, script file, or operable program

Answer 1

Get-Command can tell you this. You can even use module scope to be sure it comes from a specific module

get-command activedirectory\get-aduser -erroraction silentlycontinue

For example. Evaluate that in an if statement and you should be good to go.