Grails accessing nested fields using gstrings

Question

I am trying to access a nested field using gstring but it throws exception groovy.lang.MissingPropertyException

I have two classes

Class Person{
   Address address
}
Class Address{
  String city
}

Somewhere in my code I am doing,

def person = Person.get(1)
def field = "address.city"
def city = person."${field}"

The line where I am trying to fetch city from person is throwing groovy.lang.MissingPropertyException

If I try to fetch a direct property using gstring it works but the above given code doesnt work.

Any help?

score 12 · Accepted Answer · answered Oct 16 '11 at 13:58

12

What you're doing here is trying to access a property by name address.city which is equal to person."address.city", which means that the dot here gets considered as part of property name - not as access separator as you expect. The following code should resolve your property:

def city = field.tokenize('.').inject(person) {v, k -> v."$k"}

answered Oct 16 '11 at 13:58

Nikita Volkov

42,792
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1

That is a really elegant solution! – sbglasius Oct 17 '11 at 14:36
How do you set value of a nested property retrieved this way? – Michal Pasinski Feb 17 '13 at 00:30
@user1200125 This way you retrieve not a property reference, but it's value, so there's nothing to set a value of. – Nikita Volkov Feb 17 '13 at 06:47
any idea of how to retrieve propery/field to modify its value then? – Michal Pasinski Feb 17 '13 at 12:17
@user1200125 Nope, I'm outta groovying for more than a year now. But you can surely open a dedicated question. I think what you're looking for is reflection. – Nikita Volkov Feb 17 '13 at 13:54

score 3 · Answer 2 · answered Oct 16 '11 at 12:55

3

I think that the problem is with dot operator for access to a subproperty.

This works:

class Person{
   String address
}

def person = new Person(address:'Madrid')

def field = 'address'
assert 'Madrid' == person."${field}"

This works:

class Person{
   Address address
}

class Address {
  String city
}

def person = new Person(address: new Address(city: 'Madrid'))

def field = 'address'
def subField = 'city'
assert 'Madrid' == person."${field}"."${subField}"

answered Oct 16 '11 at 12:55

Arturo Herrero

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While I agree that the other answer by Nikita Volkov, def city = field.tokenize('.').inject(person) {v, k -> v."$k"}, IS a VERY elegant answer, I prefer the simplicity and readability of this answer. At a glance, this answer is clearly understood. – TriumphST Mar 11 '16 at 00:38

Grails accessing nested fields using gstrings

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