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Model Storage

Unlike the policy, the model can only be loaded, it cannot be saved. We believe that the model is not a dynamic component and should not be modified at runtime, so we have not implemented an API to save the model into storage.

However, there is good news. We provide three equivalent ways to load a model, either statically or dynamically:

Load model from .CONF file​

This is the most common way to use Casbin. It is easy to understand for beginners and convenient for sharing when you need help from the Casbin team.

The content of the .CONF file examples/rbac_model.conf is as follows:

[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[role_definition]
g = _, _

[policy_effect]
e = some(where (p.eft == allow))

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

Then you can load the model file as follows:

e := casbin.NewEnforcer("examples/rbac_model.conf", "examples/rbac_policy.csv")

Load model from code​

The model can be initialized dynamically from code instead of using a .CONF file. Here's an example for the RBAC model:

import (
    "github.com/casbin/casbin/v2"
    "github.com/casbin/casbin/v2/model"
    "github.com/casbin/casbin/v2/persist/file-adapter"
)

// Initialize the model from Go code.
m := model.NewModel()
m.AddDef("r", "r", "sub, obj, act")
m.AddDef("p", "p", "sub, obj, act")
m.AddDef("g", "g", "_, _")
m.AddDef("e", "e", "some(where (p.eft == allow))")
m.AddDef("m", "m", "g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act")

// Load the policy rules from the .CSV file adapter.
// Replace it with your adapter to avoid using files.
a := fileadapter.NewAdapter("examples/rbac_policy.csv")

// Create the enforcer.
e := casbin.NewEnforcer(m, a)

Load model from string​

Alternatively, you can load the entire model text from a multi-line string. The advantage of this approach is that you do not need to maintain a model file.

import (
    "github.com/casbin/casbin/v2"
    "github.com/casbin/casbin/v2/model"
)

// Initialize the model from a string.
text :=
`
[request_definition]
r = sub, obj, act

[policy_definition]
p = sub, obj, act

[role_definition]
g = _, _

[policy_effect]
e = some(where (p.eft == allow))

[matchers]
m = g(r.sub, p.sub) && r.obj == p.obj && r.act == p.act
`
m, _ := model.NewModelFromString(text)

// Load the policy rules from the .CSV file adapter.
// Replace it with your adapter to avoid using files.
a := fileadapter.NewAdapter("examples/rbac_policy.csv")

// Create the enforcer.
e := casbin.NewEnforcer(m, a)