# DEX Class

### Constructor

Instances of <mark style="color:orange;">`DEX`</mark> cannot be constructed manually. They are only accessible as a return value of <mark style="color:yellow;">`SDK.init()`</mark>. Each instance of the DEX class represents a connection to a particular instance of the Portal DEX network for a particular user.

The DEX instance returned by <mark style="color:yellow;">`SDK.init()`</mark> contains no assets. Before any trades are executed on that instance, assets must be transferred into it using <mark style="color:orange;">`DEX.xfer()`</mark>.

### Instance Properties

```javascript
Array = dex.assets
```

Returns the assets and their quantities currently available. The elements of the Array are Objects with format: `{ asset: String, qty: Number }`.

### Instance Methods

```javascript
Array = dex.xfer( source, assets )
```

Transfers one or more assets into the receiver from the specified source. Instances of DEX initially contain no assets and this method must be called before any trades are executed.

<table><thead><tr><th width="131">Argument</th><th>Type and Semantics</th></tr></thead><tbody><tr><td><mark style="color:blue;"><code>source</code></mark></td><td>Object. Specifies the source of the assets and the parameters necessary for transferring them. Format depends on the source.</td></tr><tr><td><mark style="color:blue;"><code>assets</code></mark></td><td>Array. Specifies quantities of assets to transfer. The elements of the Array are Objects with format: <code>{ asset: String, qty: Number }</code></td></tr></tbody></table>

<mark style="color:orange;">`DEX.xfer`</mark>`()` returns an Array whose elements are Objects with format:

```json
{
   status: String,
   asset: String,
   qty: Number      // quantity actually in wallet
}
```

```javascript
trade = dex.trade( order_id, order_type, goals,
                   sell_asset, sell_qty,
                   buy_asset,  buy_qty )
```

Performs a swap of the specified assets under the specified conditions. Returns an instance of the Trade class. Will throw an exception if there are any errors in the arguments - thus it is advisable to call this function in a try/catch block.

<table><thead><tr><th width="220">Argument</th><th>Type and semantics</th></tr></thead><tbody><tr><td><code>order_id</code></td><td>String (case sensitive). A user-defined identifier of this trade. Stored in the instance and returned on every method call to that instance.</td></tr><tr><td><code>order_type</code></td><td>String (case insensitive). One of: "limit" or "market".</td></tr><tr><td>goals</td><td>Object.</td></tr><tr><td><code>sell_asset, buy_asset</code></td><td>String (case insensitive). One of: "BTC" or "ETH".</td></tr><tr><td><code>sell_qty, buy_qty</code></td><td>Number</td></tr><tr><td><code>sell_ctx, buy_ctx</code></td><td>Object. Format is dependent on the values of <code>order_type</code>, <code>sell_asset</code>, and <code>buy_asset</code>.</td></tr></tbody></table>

```javascript
Boolean = dex.close()
```

Close the connection to receiver. Returns `true` if successful else `false`.

```javascript
trade = dex.find( order_id )
```

Returns the instance of Trade with the specified `order_id` or `undefined` if no trade with that `order_id` was executed on the receiver.

```javascript
Array = dex.history()
```


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