Grails Tip # 4:

No signature of method:

As specified by , Grails provides convenience method to check if a object contains errors and set the CSS class on the element.

I came across this problem where suddenly, under some conditions, I was seeing the following error:

No signature of method:

Further down the stacktrace, I notice something more interesting.

Caused by: groovy.lang.MissingMethodException: No signature of method: is applicable for argument types: (java.util.LinkedHashMap, java.lang.String) values: [[bean:{}, field:asc], input-error]Possible solutions: wait(), any(), dump(), wait(long), wait(long, int), and(java.lang.Boolean)

At first glance, the stacktrace looks like complicated garbage. However, after a few minutes of looking though the stacktrace, the parameter’s in the exception cause looked suspiciously like those specified in a invocation of the GSP’s hasErrors method.

I soon realized that this exception only occurs during situations where errors would be displayed on the GSP. Looking though the code flow, I soon realized something suspicious.

		def save = {
			if (command.hasErrors()){
				render (view:input, model:[command:command, hasErrors:true])

Notice that the if the command object has errors after validation, the model being returned to generate the GSP contains both the command and a variable hasError which is assigned to true.

I ran a quit test, what happens if try and execute the value of a boolean as a method.


And volila, a No signature of method: error. It appears, when there is a variable in the model with the same name as a GSP method, under some conditions, Grails replaces the method invocation with the value of the variable and then it executes the method.

In this example, it appears that hasErrors(…) was being replaced by the value of the hasError variable, true, and then being executed. Thus the final statement looked like the following: true(bean:command, …) This of course, would result in a no method signature found error.

After changing the name of the hasError variable to something else, say, showErrors, the GSP rendered as expected. By reading this article, I hope that you can save yourself a couple of hours of struggle.

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