Ruby

Call a JavaScript Function Returning an Integer

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Demonstrates how to call a JavaScript function that returns an integer. Ruby

require 'chilkat'

success = false

# ----------------------------------------------------------------------------------
# The Javascript function called in this example is shown at the bottom of this page.
# -----------------------------------------------------------------------------------

# In this example, we'll load the Javascript function definition from a file.
# It doesn't need to come from a file.  It could just as easily be loaded from a string.
sbScript = Chilkat::CkStringBuilder.new()
success = sbScript.LoadFile("js_call_function.js","utf-8")
if (success == false)
    print sbScript.lastErrorText() + "\n";
    exit
end

# Note: Each instance of a Chilkat Js object automatically establishes
# its own internal runtime and context.  Applications do not need to explicitly create
# the JavaScript runtime or context.
js = Chilkat::CkJs.new()

result = Chilkat::CkJsonObject.new()
result.put_EmitCompact(false)

# Call Eval to add the function (shown at the bottom of this page) to the context's global object
success = js.Eval(sbScript,result)
if (success == false)
    # Examine the result for an exception.
    print result.emit() + "\n";

    # Also examine the LastErrorText.
    print js.lastErrorText() + "\n";
    exit
end

print result.emit() + "\n";

# The expected output is "undefined":

# {
#   "type": "undefined",
#   "value": "undefined"
# }

#    When Eval processes a script containing only a function declaration,
#    it successfully performs the action (the function becomes defined).
#    However, since the script consists of a statement that produces no value,
#    the script's overall completion value is empty. In JavaScript, the
#    absence of a value is represented by `undefined`.
# 
#    Therefore, the Eval call returns `undefined`.

# ------------------------------------------------------------------------------
# Call the function calculateScore("Player1", 10, 20)

funcCall = Chilkat::CkJsonObject.new()

# Create JSON defining the function call:

# {
#   "name": "calculateScore",
#   "args": [ "Player1", 10, 20 ]
# }

funcCall.UpdateString("name","calculateScore")
funcCall.UpdateString("args[0]","Player1")
funcCall.UpdateInt("args[1]",10)
funcCall.UpdateInt("args[2]",20)

funcCall.put_EmitCompact(false)
print funcCall.emit() + "\n";

success = js.CallFunction(funcCall,result)
if (success == false)
    # Examine the result for an exception.
    print result.emit() + "\n";

    # Also examine the LastErrorText.
    print js.lastErrorText() + "\n";
    exit
end

print result.emit() + "\n";

# Output:

# {
#   "type": "int",
#   "value": 37
# }

retval = result.IntOf("value")
print "retval = " + retval.to_s() + "\n";