Mounting a spec

In redux you can combine reducers and made them apply to specific parts of the state by using combineReducers. The equivalent functionality in redux-capi is called mounting though it can do much more. Mounting is establishing a state path that is the starting point (mount point) for an API spec. It can be specified:

• When you mount the API into the store
• As part of declaring the spec though usually that would be when composing a spec from other specs The state graph looks exactly like the schema in a redaction except that the last property is set to the boolean true value.

mountPoint = {
    data: {
        telephones: {
            list: true
        }
    }
}

When this mount point is applied to a spec as in

myAPI.mount(store, mountPoint)

all references to the list property in spec will refer to data.telephones.list. This means:

• The list property in the schema in all redactions
• Any state passed to the functions within the schema will be relative list rather than data.telephones.list

This means that the spec can be completely unaware of where exactly in the state shape the properties it is dealing with actually reside. This makes it possible to re-use specs and to organize state shape in a large application without naming conflicts.

Using Arrays in Mount Points

There may be times when you want to use spec and mount it into an array element. Suppose you have multiple lists and a current one. You want the spec to only apply to the current one. In that case you can use where just as you would in a redaction to qualify which element of the array the spec is to apply to.

mountPoint = {
    todoLists: {
         where: (state, item, ix, api) => state.currentListIx === ix
    }
}

or you may have multiple levels of arrays by nesting where and optionally select as for redactions:

mountPoint = {
    companies: {
        where: where: (state, item, ix, api) => state.companyIx == Ix,
        select: {
            todoLists: {
                 where: (state, item, ix, api) => 
                        state.companies[state.companyIx].listIx === ix,
            }
        }
    }
}