Summary of my iOS issues

1 The Settitle,titlelabel difference of UIButton. How to get the pixel length of the label.

Other people's problems:

First of all, thank you very much for your answer. Secondly, I have a little doubt, as follows: effect comparison (handwriting button):
1, [But settitle:@ "test" forstate:uicontrolstatenormal];
Output: Currenttitlelabel: Test it, Currenttitle: Test it. The simulator button displays: Test
2, But.titlelabel.text = @ "Test";
Output: Currenttitlelabel: Test, Currenttitle: (null). No Display on simulator button
3, [But settitle:@ "test" forstate:uicontrolstatenormal];
But.titlelabel.text = @ "Test Two";
Output: Currenttitlelabel: Test Two, Currenttitle: Test a bit. Simulator button on display: Test two
4, But.titlelabel.text = @ "Test Two";
[But settitle:@ "test" forstate:uicontrolstatenormal];
Output: Currenttitlelabel: Test it, Currenttitle: Test it. The simulator button displays: Test
Do not understand the situation in 3! Solving......

Summary of my iOS issues