87 lines
No EOL
2.4 KiB
Markdown
87 lines
No EOL
2.4 KiB
Markdown
## m.prop
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This is a getter-setter factory utility. It returns a function that stores information
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---
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### Usage
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```javascript
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//define a getter-setter with initial value `John`
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var name = m.prop("John");
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//read the value
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var a = name(); //a == "John"
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//set the value to `Mary`
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name("Mary"); //Mary
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//read the value
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var b = name(); //b == "Mary"
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```
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It can be used in conjunction with [`m.withAttr`](mithril.withattr) to implement data binding in the view-to-model direction and to provide uniform data access for model entity properties.
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```javascript
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//a contrived example of bi-directional data binding
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var user = {
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model: function(name) {
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this.name = m.prop(name);
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},
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controller: function() {
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this.user = new user.model("John Doe");
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},
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view: function(controller) {
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m.render("body", [
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m("input", {onchange: m.withAttr("value", controller.user.name), value: controller.user.name()})
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]);
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}
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};
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```
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In the example above, the usage of `m.prop` allows the developer to change the implementation of the user name getter/setter without the need for code changes in the controller and view.
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`m.prop` can also be used in conjunction with [`m.request`](mithril.request) and [`m.deferred`](mithril.deferred) to bind data on completion of an asynchronous operation.
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```javascript
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var users = m.prop([]);
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var error = m.prop("");
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m.request({method: "GET", url: "/users"})
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.then(users, error); //on success, `users` will be populated, otherwise `error` will be populated
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//assuming the response contains the following data: `[{name: "John"}, {name: "Mary"}]`
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//then when resolved (e.g. in a view), the `users` getter-setter will contain a list of User instances
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//i.e. users()[0].name() == "John"
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```
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---
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### Signature
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[How to read signatures](how-to-read-signatures.md)
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```clike
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GetterSetter prop([any initialValue])
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where:
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GetterSetter :: any getterSetter([any value])
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```
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- **any initialValue** (optional)
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An initialization value. If not provided, the value of the getter-setter's internal store defaults to `undefined`.
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- **returns any getterSetter([any value])**
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A getter-setter method.
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- **any value** (optional)
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If provided, it updates the getter-setter's internal store to the provided value.
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If not provided, return the current internally stored value.
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- **returns any value**
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This method always returns the value of the internal store, regardless of whether it was updated or not.
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