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event handling example tweaks: consistent form for event-handling.

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walterhiggins 2015-01-11 00:46:55 +00:00
parent 2e7dfb2453
commit d73ab1a083
2 changed files with 88 additions and 74 deletions
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37
docs/YoungPersonsGuideToProgrammingMinecraft.md
View file

@ -926,15 +926,16 @@ pointing at the block, type the following into the in-game prompt...
so the next step is to repeat this over and over. This is where `for` so the next step is to repeat this over and over. This is where `for`
loops come in. Open your favorite text editor and create a new file in loops come in. Open your favorite text editor and create a new file in
your scriptcraft/plugins/{your-name} directory, name the file `myskyscraper.js`, then your scriptcraft/plugins/{your-name} directory, name the file `myskyscraper.js`, then
type the following... type the following code and save:
```javascript ```javascript
var myskyscraper = function(floors) { function myskyscraper( floors ) {
var i ; var i ;
if ( typeof floors == 'undefined' ) { if ( typeof floors == 'undefined' ) {
floors = 10; floors = 10;
} }
this.chkpt('myskyscraper'); // saves the drone position so it can return there later // bookmark the drone's position so it can return there later
this.chkpt('myskyscraper');
for ( i = 0; i < floors; i++ ) { for ( i = 0; i < floors; i++ ) {
this this
.box(blocks.iron,20,1,20) .box(blocks.iron,20,1,20)
@ -942,13 +943,14 @@ var myskyscraper = function(floors) {
.box0(blocks.glass_pane,20,3,20) .box0(blocks.glass_pane,20,3,20)
.up(3); .up(3);
} }
this.move('myskyscraper'); // return to where we started // return the drone to where it started
this.move('myskyscraper');
}; };
var Drone = require('drone'); var Drone = require('drone');
Drone.extend( myskyscraper ); Drone.extend( myskyscraper );
``` ```
... so this takes a little explaining. First I create a new function So this takes a little explaining. First I create a new function
called myskyscraper that will take a single parameter `floors` so that called myskyscraper that will take a single parameter `floors` so that
when you eventually call the `myskyscraper()` function you can tell it when you eventually call the `myskyscraper()` function you can tell it
how many floors you want built. The first statement in the function how many floors you want built. The first statement in the function
@ -963,11 +965,11 @@ The last 2 lines load the drone module (it must be loaded before I can
add new features to it) and the last line extends the 'Drone' object add new features to it) and the last line extends the 'Drone' object
so that now it can build skyscrapers among other things. Once you've so that now it can build skyscrapers among other things. Once you've
typed in the above code and saved the file, type `/js refresh()` in your typed in the above code and saved the file, type `/js refresh()` in your
in-game prompt, then type ... in-game prompt, then type:
/js myskyscraper(2); /js myskyscraper(2);
... A two-story skyscraper should appear. If you're feeling A two-story skyscraper should appear. If you're feeling
adventurous, try a 10 story skyscraper! Or a 20 story skyscraper! adventurous, try a 10 story skyscraper! Or a 20 story skyscraper!
Minecraft has a height limit (256 blocks from bedrock) beyond which Minecraft has a height limit (256 blocks from bedrock) beyond which
you can't build. If you try to build higher than this then building you can't build. If you try to build higher than this then building
@ -987,11 +989,11 @@ All the programs we have seen so far have been fairly predictable - they went
straight through the statements, and then went back to the beginning again. This is straight through the statements, and then went back to the beginning again. This is
not very useful. In practice the computer would be expected to make decisions and not very useful. In practice the computer would be expected to make decisions and
act accordingly. The javascript statement used for making decisions is `if`. act accordingly. The javascript statement used for making decisions is `if`.
While standing on the ground in-game, type the following at the command prompt... While standing on the ground in-game, type the following at the command prompt:
/js if ( self.onGround ) { echo('You are not flying!'); } /js if ( self.onGround ) { echo('You are not flying!'); }
the following message should have appeared on your screen... the following message should have appeared on your screen:
You are not flying! You are not flying!
@ -1003,7 +1005,7 @@ keyboard, the statement you entered previously should reappear.
/js if ( self.onGround ) { echo('You are not flying!'); } /js if ( self.onGround ) { echo('You are not flying!'); }
... this time no message should appear on your screen. This time no message should appear on your screen.
The `if` statement tests to see if something is `true` or `false` and The `if` statement tests to see if something is `true` or `false` and
if `true` then the block of code between the curly braces ( `{` and if `true` then the block of code between the curly braces ( `{` and
@ -1012,11 +1014,11 @@ in the above example is `!self.onGround` (self is not on ground) which
will be `true` if you are currently flying or `false` if you aren't. will be `true` if you are currently flying or `false` if you aren't.
What if you wanted to display a message only if a condition is *not* What if you wanted to display a message only if a condition is *not*
true ? For example to only display a message if the player is *not* on the ground... true ? For example to only display a message if the player is *not* on the ground:
/js if ( !self.onGround ) { echo ('You are flying!'); } /js if ( !self.onGround ) { echo ('You are flying!'); }
... This code differs in that now there's a `!` (the exclamation mark) This code differs in that now there's a `!` (the exclamation mark)
before `self.onGround`. The `!` symbol negates (returns the opposite of) before `self.onGround`. The `!` symbol negates (returns the opposite of)
whatever follows it. whatever follows it.
@ -1098,11 +1100,12 @@ just specify the fully qualified class name instead. E.g. ...
If you want an event handler to only execute once, you can remove the handler like this... If you want an event handler to only execute once, you can remove the handler like this...
```javascript ```javascript
events.blockDestroy( function( evt ) { function myBlockDestroyHook( evt ) {
var breaker = evt.player; var breaker = evt.player;
echo( breaker, 'You broke a block'); echo( breaker, 'You broke a block');
this.unregister(); this.unregister();
} ); }
events.blockDestroy( myBlockDestroyHook );
``` ```
The `this.unregister();` statement will remove this function from the The `this.unregister();` statement will remove this function from the
@ -1114,7 +1117,11 @@ to stop listening for events.
To unregister a listener *outside* of the listener function... To unregister a listener *outside* of the listener function...
```javascript ```javascript
var myBlockBreakListener = events.blockDestroy(function( evt ) { ... } ); function myBlockDestroyHook( evt ){
var breaker = evt.player;
echo( breaker, 'You broke a block');
}
var myBlockBreakListener = events.blockDestroy( myBlockDestroyHook );
... ...
myBlockBreakListener.unregister(); myBlockBreakListener.unregister();
``` ```

37
src/docs/templates/ypgpm.md vendored
View file

@ -884,15 +884,16 @@ pointing at the block, type the following into the in-game prompt...
so the next step is to repeat this over and over. This is where `for` so the next step is to repeat this over and over. This is where `for`
loops come in. Open your favorite text editor and create a new file in loops come in. Open your favorite text editor and create a new file in
your scriptcraft/plugins/{your-name} directory, name the file `myskyscraper.js`, then your scriptcraft/plugins/{your-name} directory, name the file `myskyscraper.js`, then
type the following... type the following code and save:
```javascript ```javascript
var myskyscraper = function(floors) { function myskyscraper( floors ) {
var i ; var i ;
if ( typeof floors == 'undefined' ) { if ( typeof floors == 'undefined' ) {
floors = 10; floors = 10;
} }
this.chkpt('myskyscraper'); // saves the drone position so it can return there later // bookmark the drone's position so it can return there later
this.chkpt('myskyscraper');
for ( i = 0; i < floors; i++ ) { for ( i = 0; i < floors; i++ ) {
this this
.box(blocks.iron,20,1,20) .box(blocks.iron,20,1,20)
@ -900,13 +901,14 @@ var myskyscraper = function(floors) {
.box0(blocks.glass_pane,20,3,20) .box0(blocks.glass_pane,20,3,20)
.up(3); .up(3);
} }
this.move('myskyscraper'); // return to where we started // return the drone to where it started
this.move('myskyscraper');
}; };
var Drone = require('drone'); var Drone = require('drone');
Drone.extend( myskyscraper ); Drone.extend( myskyscraper );
``` ```
... so this takes a little explaining. First I create a new function So this takes a little explaining. First I create a new function
called myskyscraper that will take a single parameter `floors` so that called myskyscraper that will take a single parameter `floors` so that
when you eventually call the `myskyscraper()` function you can tell it when you eventually call the `myskyscraper()` function you can tell it
how many floors you want built. The first statement in the function how many floors you want built. The first statement in the function
@ -921,11 +923,11 @@ The last 2 lines load the drone module (it must be loaded before I can
add new features to it) and the last line extends the 'Drone' object add new features to it) and the last line extends the 'Drone' object
so that now it can build skyscrapers among other things. Once you've so that now it can build skyscrapers among other things. Once you've
typed in the above code and saved the file, type `/js refresh()` in your typed in the above code and saved the file, type `/js refresh()` in your
in-game prompt, then type ... in-game prompt, then type:
/js myskyscraper(2); /js myskyscraper(2);
... A two-story skyscraper should appear. If you're feeling A two-story skyscraper should appear. If you're feeling
adventurous, try a 10 story skyscraper! Or a 20 story skyscraper! adventurous, try a 10 story skyscraper! Or a 20 story skyscraper!
Minecraft has a height limit (256 blocks from bedrock) beyond which Minecraft has a height limit (256 blocks from bedrock) beyond which
you can't build. If you try to build higher than this then building you can't build. If you try to build higher than this then building
@ -945,11 +947,11 @@ All the programs we have seen so far have been fairly predictable - they went
straight through the statements, and then went back to the beginning again. This is straight through the statements, and then went back to the beginning again. This is
not very useful. In practice the computer would be expected to make decisions and not very useful. In practice the computer would be expected to make decisions and
act accordingly. The javascript statement used for making decisions is `if`. act accordingly. The javascript statement used for making decisions is `if`.
While standing on the ground in-game, type the following at the command prompt... While standing on the ground in-game, type the following at the command prompt:
/js if ( self.onGround ) { echo('You are not flying!'); } /js if ( self.onGround ) { echo('You are not flying!'); }
the following message should have appeared on your screen... the following message should have appeared on your screen:
You are not flying! You are not flying!
@ -961,7 +963,7 @@ keyboard, the statement you entered previously should reappear.
/js if ( self.onGround ) { echo('You are not flying!'); } /js if ( self.onGround ) { echo('You are not flying!'); }
... this time no message should appear on your screen. This time no message should appear on your screen.
The `if` statement tests to see if something is `true` or `false` and The `if` statement tests to see if something is `true` or `false` and
if `true` then the block of code between the curly braces ( `{` and if `true` then the block of code between the curly braces ( `{` and
@ -970,11 +972,11 @@ in the above example is `!self.onGround` (self is not on ground) which
will be `true` if you are currently flying or `false` if you aren't. will be `true` if you are currently flying or `false` if you aren't.
What if you wanted to display a message only if a condition is *not* What if you wanted to display a message only if a condition is *not*
true ? For example to only display a message if the player is *not* on the ground... true ? For example to only display a message if the player is *not* on the ground:
/js if ( !self.onGround ) { echo ('You are flying!'); } /js if ( !self.onGround ) { echo ('You are flying!'); }
... This code differs in that now there's a `!` (the exclamation mark) This code differs in that now there's a `!` (the exclamation mark)
before `self.onGround`. The `!` symbol negates (returns the opposite of) before `self.onGround`. The `!` symbol negates (returns the opposite of)
whatever follows it. whatever follows it.
@ -1056,11 +1058,12 @@ just specify the fully qualified class name instead. E.g. ...
If you want an event handler to only execute once, you can remove the handler like this... If you want an event handler to only execute once, you can remove the handler like this...
```javascript ```javascript
events.blockDestroy( function( evt ) { function myBlockDestroyHook( evt ) {
var breaker = evt.player; var breaker = evt.player;
echo( breaker, 'You broke a block'); echo( breaker, 'You broke a block');
this.unregister(); this.unregister();
} ); }
events.blockDestroy( myBlockDestroyHook );
``` ```
The `this.unregister();` statement will remove this function from the The `this.unregister();` statement will remove this function from the
@ -1072,7 +1075,11 @@ to stop listening for events.
To unregister a listener *outside* of the listener function... To unregister a listener *outside* of the listener function...
```javascript ```javascript
var myBlockBreakListener = events.blockDestroy(function( evt ) { ... } ); function myBlockDestroyHook( evt ){
var breaker = evt.player;
echo( breaker, 'You broke a block');
}
var myBlockBreakListener = events.blockDestroy( myBlockDestroyHook );
... ...
myBlockBreakListener.unregister(); myBlockBreakListener.unregister();
``` ```