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Functions in matchers

You can even specify functions in a matcher to make it more powerful. You can use the built-in functions or specify your own function. All built-in functions take such a format(except keyGet and keyGet2):

bool function_name(string arg1, string arg2)

It returns whether arg1 matches arg2.

keyGet and keyGet2 will return the string which matching the wildcard, and return "" if nothing was matched.

The supported built-in functions are:

Function	arg1	arg2	Example
keyMatch	a URL path like /alice_data/resource1	a URL path or a * pattern like /alice_data/*	keymatch_model.conf/keymatch_policy.csv
keyGet	a URL path like /alice_data/resource1	a URL path or a * pattern like /alice_data/*	keyget_model.conf/keymatch_policy.csv
keyMatch2	a URL path like /alice_data/resource1	a URL path or a : pattern like /alice_data/:resource	keymatch2_model.conf/keymatch2_policy.csv
keyGet2	a URL path like /alice_data/resource1	a URL path or : pattern like /alice_data/:resource	keyget2_model.conf/keymatch2_policy.csv
keyMatch3	a URL path like /alice_data/resource1	a URL path or a {} pattern like /alice_data/{resource}
keyMatch4	a URL path like /alice_data/123/book/123	a URL path or a {} pattern like /alice_data/{id}/book/{id}
regexMatch	any string	a regular expression pattern	keymatch_model.conf/keymatch_policy.csv
ipMatch	an IP address like 192.168.2.123	an IP address or a CIDR like 192.168.2.0/24	ipmatch_model.conf/ipmatch_policy.csv

See details for above functions at: https://github.com/casbin/casbin/blob/master/util/builtin_operators_test.go

How to add a customized function

First prepare your function. It takes several parameters and return a bool:

func KeyMatch(key1 string, key2 string) bool {
    i := strings.Index(key2, "*")
    if i == -1 {
        return key1 == key2
    }

    if len(key1) > i {
        return key1[:i] == key2[:i]
    }
    return key1 == key2[:i]
}

Then wrap it with interface{} types:

func KeyMatchFunc(args ...interface{}) (interface{}, error) {
    name1 := args[0].(string)
    name2 := args[1].(string)

    return (bool)(KeyMatch(name1, name2)), nil
}

At last, register the function to the Casbin enforcer:

e.AddFunction("my_func", KeyMatchFunc)

Now, you can use the function in your model CONF like this:

[matchers]
m = r.sub == p.sub && my_func(r.obj, p.obj) && r.act == p.act