遊戯王電卓アプリ

swiftで練習がてら遊戯王の電卓を作ってみたのですが、
コメント//ここでエラー
の箇所で以下のようなエラー文が出ました

Thread 1: EXC_BAD_INSTRUCTION(code=EXC_1386_INVOP,subcode=0X0)

なぜこのようなことになるのでしょうか？
タイミングとしてはアプリをシュミレータで起動後、数字ボタンを押したときにおきます。

lang
1
2import UIKit
3
4class ViewController: UIViewController {
5
6    override func viewDidLoad() {
7        super.viewDidLoad()
8        // Do any additional setup after loading the view, typically from a nib.
9    }
10
11    override func didReceiveMemoryWarning() {
12        super.didReceiveMemoryWarning()
13        // Dispose of any resources that can be recreated.
14    }
15
16    @IBOutlet weak var Player1Display: UILabel!
17
18    @IBOutlet weak var Player2Display: UILabel!
19    
20    @IBOutlet weak var operation: UILabel!
21
22    var playerSpecified: Int!
23    
24    var result: Int! = nil
25    var currentNumStr = ["",""]
26    var currentOpe: String! = nil
27    
28    
29    @IBOutlet weak var segmentedControl: UISegmentedControl!
30    
31    func setLabelResult(info: (val: Int, error: String?)) {
32        var text: String = "\(info.val)"
33        if (info.error != nil) {
34            calcClear()
35            text = info.error!
36        }
37        if playerSpecified == 0 {
38            Player1Display.text = text
39        } else {
40            Player2Display.text = text
41        }
42    }
43    
44    func setLabelOpe() {
45        var text = ""
46        if currentOpe != nil {
47            text = "\(currentOpe)"
48        }
49        operation.text = text
50            }
51    
52    func calcInit() {
53        calcClear()
54        setLabelResult((8000,nil))
55    }
56    
57    func calcClear() {
58        result = nil
59        if playerSpecified == 0 {
60            currentNumStr[0] = ""
61        } else {
62            currentNumStr[1] = ""
63        }
64        currentOpe = nil
65        setLabelOpe()
66    }
67    
68    func calc(num1: Int,ope: String,num2: Int) -> (Int,String?) {
69        
70        let calcFuncs:[String: (Int,Int) -> (Int,String?)] = [
71            "=": calc_eq,
72            "+": calc_add,
73            "-": calc_sub
74        ]
75        
76        return calcFuncs[ope]!(num1,num2)
77    }
78    
79    func calc_eq(num1: Int,num2: Int) -> (Int,String?) {
80        return (num2,nil)
81    }
82    func calc_add(num1: Int,num2: Int) -> (Int,String?) {
83        return (num1 + num2,nil)
84    }
85    func calc_sub(num1: Int,num2: Int) -> (Int,String?) {
86        return (num1 - num2,nil)
87    }
88    
89    @IBAction func btnNumber(sender: UIButton) {
90        let v = sender.titleLabel?.text!
91        if v == "0" {
92            if currentNumStr[playerSpecified] != "" {
93                currentNumStr[playerSpecified] = currentNumStr[playerSpecified] + v!
94            } else {
95                currentNumStr[playerSpecified] = "0"
96            }
97        } else {
98            //ここでエラー
99            currentNumStr[playerSpecified] = currentNumStr[playerSpecified] + v!
100        }
101        
102        var x: Int = 0
103        if currentNumStr[playerSpecified] != "" {
104            x = currentNumStr[playerSpecified].toInt()!
105        }
106        setLabelResult((x,nil))
107
108    }
109    
110    @IBAction func btnOperate(sender: UIButton) {
111        var v = sender.titleLabel?.text
112        var rets: (val: Int,error: String?) = (0,nil)
113        
114        if result != nil && currentNumStr[playerSpecified] != "" && currentOpe != nil {
115            rets = calc(result, ope: currentOpe, num2: currentNumStr[playerSpecified].toInt()!)
116            setLabelResult(rets)
117            if rets.error == nil {
118                result = rets.val
119            }
120            currentNumStr[playerSpecified] = ""
121        } else {
122            if currentNumStr[playerSpecified] != "" {
123                result = currentNumStr[playerSpecified].toInt()!
124            }
125            currentNumStr[playerSpecified] = ""
126        }
127        
128        if v == "=" {
129            currentOpe = nil
130        } else {
131            currentOpe = v
132        }
133        setLabelOpe()
134    }
135    
136    @IBAction func btnClear(sender: UIButton) {
137        calcInit()
138    }
139    
140    //プレイヤー切り替え
141    @IBAction func changePlayer(sender: UISegmentedControl) {
142        switch segmentedControl.selectedSegmentIndex {
143        case 0 : playerSpecified = 0
144                println("playerSpecified is \(playerSpecified)")
145        case 1 : playerSpecified = 1
146                println("playerSpecified is \(playerSpecified)")
147        default : break
148        }
149        
150    }
151    
152    
153    
154    
155    
156    
157}